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FAQs on Reverse Osmosis for Freshwater Aquariums

Related Articles: Water Quality, pH, alkalinity, acidityTreating Tap Water, Freshwater Aquarium Water Quality, Freshwater Maintenance

Related FAQs:  Fresh water QualityTreating Tap Water for Aquarium Use, Reverse Osmosis for Freshwater, pH, Alkalinity, Acidity, Freshwater Algae Control, Algae Control, Foods, Feeding, Aquatic Nutrition, Disease

A nice FW set up in Germany... Ambulia and Cardinals mainly.

RO/DI waste water, Oscar sys.     1/14/13
Good morning
I have BRS 75gpd 4stage ro/di system for my 125 gallon fowlr. I also have a 75 gallon tank with 1 Oscar , I heard I should not use ro/di in the Oscar tank.
<Mmm, likely yes; Astronotus live well enough in most potable waters of moderate hardness, alkalinity... pH. What is your tap water like?>
 My question is should I use the waste water or just tap water with a dechlorinator when doing water changes to the Oscar tank?
<Again; likely the latter, depending on its water qualities. The vented "waste water" from the RO/DI may be useful... but I'd use it on plants. Bob Fenner>

Water Softener, Arowana - 12/29/2012
thanks for your reply
<You're welcome.  Sabrina here tonight.>
i am using water  softener for domestic purpose,  is the water from water softener can we use for the aquarium .
<Preferably not, no.>
iam having silver Arowana the drawback from water softener is , it provides sodium chloride (saltywater),
<You are correct.  This is not optimal.  Although I do not know what your tapwater is like where you are in India, here (I am in the US) we typically have chlorine or chloramine added to the city water, and then people sometimes use water softeners for their houses for domestic purposes (like you are doing).  What we usually suggest to them is to use water from before it goes through the softener, and then to use a proper chlorine/chloramine neutralizer sold for aquarium use.>
whether salt water is good for silver Arowana , it will not be much salty.
<The biggest problem is that as you replace water that evaporates, you're going to be increasing the amount of salts in the water.  This is not ideal.>
give your suggestion
<If possible, use fresh tapwater, and use a chlorine or chloramine neutralizer, if these are added by your municipality. 
Best wishes to you,  -Sabrina>

RODI water and salt mixes    1/18/12
Hello Crew, Neale to be specific.
This is Eric and I have a question about using salt mixes in conjunction with RODI water for use in freshwater aquariums. I am going to start using RODI water for my freshwater tanks due to the fact that my tap water has nitrates in it.
<Not necessarily a killer. Cichlids, especially Tanganyikans and Dwarf Cichlids need less than 20 mg/l, but barbs, tetras, and so on will be fine up to 50 mg/l, and the hardier species like Danios and Ricefish can handle up to 100 mg/l! Fast-growing plants can remove nitrate at an astonishing rate, so lightly-stocked aquaria with fast-growing plants (e.g., Indian Fern) can provide remarkably good water quality.>
I am using this salt mix recipe for making the water. Per 5 US Gallons, one half level teaspoons Baking Soda, one half level tablespoon Epsom Salt, and one half level teaspoon Marine Salt. I added the mix to a 5 Gallon bucket with RODI water, aerated and circulated it for 2 hours then tested the water for pH, KH, and GH. These were my results - pH 7.6, GH 160 mg/l, KH 70 mg/l. Any Ideas what I can do to get these parameters to were I need them for my tanks?
<Depends what you want to keep. But good middle-of-the-road values would be these: general hardness 100-150 mg/l; carbonate hardness 50-100 mg/l; and a pH between 7 and 7.5. Such water would suit all but the most sensitive South American and Southeast Asian fish, and would also be acceptable for this fish that dislike soft water, such as Platies and Guppies. Your water isn't very far off this range, so you might simply mix 3 parts tap water with 1 part RO water. That'd be economical and should be effective. You might go to 2 parts tap to 1 part RO if you wanted softer water. Obviously less adaptable fish, such as Mollies (which need very alkaline water) or Common Ram Cichlids (which need very acidic water) will need conditions outside this range. Review, and act accordingly.>
These are what I have in my tanks, one 75 gallon tank with a Flowerhorn Cichlid, one 75 gallon tank with three red tail
tinfoil barbs, two Pictus catfish and one common Pleco, and one 46 gallon tank with 3 rose barbs, three blue gouramis, three kissing gouramis, one common Pleco and one Asian sucker. Thank You for all the wonderful help that I have received from this great website!!
<Hope this helps. Cheers, Neale.>
Re: RODI water and salt mixes, for FW use     1/18/12

Well i am looking at using only RODI water for these aquariums no tap water, so with the values that I gave you in the previous e-mail what do you think I need to add to, or subtract from the salt mix to get within the right values from the different fish and aquariums that  I listed in the previous email?
<A "teaspoon" isn't a scientific unit, so we can't predict how much general hardness or carbonate hardness you'd get from adding 3 teaspoons of Epsom salt or one teaspoon of sodium bicarbonate. Instead, you have to experiment. Add the salt mix to a bucket of water, stir, test, and write down the values. If it isn't right, repeat, with more or less of each of the three salt mix ingredients, understanding that Epsom salt changes general hardness, sodium bicarbonate carbonate hardness, and marine salt mix a little bit of both.>
Here is a recap of what I have in my aquariums
75 gallon tank with a Flowerhorn Cichlid and a Common Plecostomus 75 gallon tank with three Red Tail Tinfoil Barbs, two Pictus Catfish and one Common Plecostomus
46 gallon tank with three Rose Barbs, three Blue Gouramis, three Kissing Gouramis, one Common Plecostomus and one Asian Sucker.
Thank You again
<Cheers, Neale.>
Re: RODI water and salt mixes    1/18/12

Thank You so much Neale, I truly appreciate all the help and insight I have received from you and Wet Web Media.
<Happy to help. Good luck, Neale.>

: Help... Not in your articles !  Induced RO issues, FW...  - 8/17/10
So sorry to bother you once again, but I have lost so many exquisite fish and I'm ready to give up.
<I see.>
I can't see them die anymore. I've literally spent thousands of dollars
trying to understand the science of how to manage these water parameters and it seems ultimately impossible. I write one more time to see if you have any further ideas.
I have ornamental goldfish ... 3 in a 55 G and 3 in a 75 G.
I have Canister filters and HOB plus underwater pump on each tank. There is heavy filtration, bio media and surface movement. Water changes every 5 days religiously with vacuuming and no overfeeding.
My fish are floaters on pellets, so they get veggies and some raw shrimp. My tanks are clean and tested every day, ammonia, nitrite and nitrate are kept at 0 with water changes and Nitrazorb.
city water
PH 9.8
<Much too high.>
KH 53
GH 71
calcium undetectable on a test.
<I see.>
I put in a 3 stage reverse osmosis unit in my house... but the PH is still outrageously high, at 9.8.
<This doesn't make sense. Are you sure it's an RO unit? A domestic water softener IS NOT an RO filter. Domestic water softeners merely remove carbonate and bicarbonate salts that create limescale. If you do have an RO unit, if it's not producing water with 0 KH, 0 GH, and pH 7 then your unit isn't working correctly, either because of configuration or maintenance.>
The city water and RO water both behave the same.
<Which shouldn't be the case.>
If I age the water in large tubs for 4-5 days, the PH drops to around 8. When it is added to an aquarium, and a PH of 8 is established with KH at 160, GH at 200, the Ph begins to rebound back up every single day until within a week, the PH is up to 9.8 again and my fish are dying. (no more vacations)
What am I missing in the buffering that I cannot stabilise the PH? I am out of ideas and I've resorted to using Acid Buffer by Seachem to try to hold the PH by adding the recommended amount every day or every other day.
<No no no'¦ don't use "pH down" products in this way; acid buffers are to hold an acidic pH, not to create one. It's a shame the manufacturers are a bit disingenuous about this.>
Sometimes it works but too often, it is unpredictable and I have a yoyo Ph.... this method of controlling PH is volatile, unpredictable and obviously unacceptable.
The fish become lethargic and unhappy until I change water again at day 5. I have had problems with Flukes/gill Ich and white edges on fins from bottom sitting. After eating, every fish is desperate for oxygen and gobble bubbles frantically until after an hour of this, they begin to float upside down from all of the bubbles they have swallowed. The amount of filtration and splashing in my tanks is ridiculous... the sound is like living under Niagara Falls. I know this all has to be due to the erratic water parameters.
I have been using the Rift Valley mix, with half RO and half tap water, as Neale suggested.
<Which will work perfectly if you're starting with true RO water. Indeed, a bucket of pure RO water, with about 25-50% the Rift Valley salt mix added should create something good for a broad range of species, around pH 7.5, general hardness around 10 degrees dH. But if the RO water isn't 0 general hardness, 0 carbonate hardness, and pH 7, then obviously this isn't going to work.>
But with the nightmare of dead fish continuing, I stopped using Rift Valley and switched to Lake Malawi salts (Seachem) hoping that it would have a broader buffer content.....but it takes A LOT of it to bring the KH and GH up.... and doesn't do enough to drop the PH.
<Again, should work fine with RO water. The Seachem product is much the same as the DIY Rift Valley mix in terms of result, just cheaper. On the plus side, with the Rift Valley mix, you can tweak the Epsom salt and baking soda up or down to raise or lower the GH or KH values respectively.>
I end up with my KH too high and the Ph still at 8.8. So I have resorted to using Seachem Acid Buffer just to try to get the PH down. But I cannot hold the PH no matter what I do, and the stress on my fish is deadly. Even when KH and GH are within good parameters, there is no calcium in the water, I discovered 2 weeks ago. I never previously had a specific test for Calcium, and only concerned myself with KH and GH. I bought Aquavitro Calcification and have slowly been trying to raise the calcium. It is just below 100 now today.
<Let me stress that your problem IS NOT what you're adding to your water. Whether you use the Rift Valley mix, the Seachem product, or any other buffering mix, when added to RO water at about 50% the dose for Malawi cichlids, you should get something more or less perfect for Goldfish. But your problem is that your supposed RO filter is not producing RO water. THAT is your problem. Establish what's wrong with your RO filter, and once it's producing pure water, with 0 general hardness, 0 carbonate hardness, and a pH around 7.0, then you'll be all set.>
Here is a direct link to our city water analysis, but these parameters tend to fluctuate.. Only the Ph remains at 9.7 and sometimes as high as 10. Three months ago the GH was over 300, and now it is extremely low.
Please if you have any suggestions or can recommend a further strategy, please help. I would do whatever it takes to keep these fish healthy... I know there have to be answers, but I just can't watch any more fish dropsy and die when I am gone for a weekend.
Thank you,
<Amy, do please read here and the articles linked at the end of the piece. There is something very amiss with your RO system.
Apart from maybe Malawian or Rift Valley cichlids, or else Central American livebearers and Goodeids, I can't think of any fish that will thrive in water at pH 9, 200 mg/l dH. Cheers, Neale.>

Buffering RO with decor.   6/22/10
Hi guys (Neale?)
I didn't get a response to my last email a week ago perhaps due to my poor grammar or am I being impatient?
<Funnily enough, yesterday someone else mentioned -- actually, complained loudly! -- the lack of response. Possibly more than one message didn't arrive?>
Electronics is my subject so I hope you can excuse my below average English skills.
<Will do my best.>
I recently asked some questions about hard plumbing a 570 liter fresh water divider tank with a canister filter and it's now complete and just starting to cycle.
<Cool. Nice size tank, by the way; for our US readers, about 150 of their Earth gallons.>
The problem is the local water quality here is pretty dire so I have invested in an RO filter which actually worked out cheaper both initially and long term than a DI filter.
<Can well be, though does depend on your usage. In your case yes, an RO filter may well pay for itself. If you only have a small aquarium, rainwater can often be collected adequately well to supply your needs.
That's what I do, and mixed 50/50 with tap water, is enough for about 250 litres' worth of aquaria.>
The local water we have (Jersey Channel Islands) peaks at over 70 Nitrate with a very high TDS content and contains low levels of Ammonia straight from the tap.
<I see. Again, not a killer, but I can see how you'd want to avoid processing this into aquarium water.>
I am using the RO water straight at this stage (no fish yet) which is still at 10 ppm TDS after filtering.
<Do make sure the RO filter is operating properly. Among other things, you tend to need at least one carbon pre-filter and often more than one RO filter canister. Do read here:
Then I am adding Microbe-Lift R/O Water Conditioner to replace missing elements.
<OK, but in and of itself this may not be adequate for the fish you're keeping. Do research the fish you want to keep, and add minerals accordingly. For a general mixed community of tropical fish, the ideal water chemistry is about 10 degrees dH general hardness, and a pH between 7 and 7.5. I'd recommend using the Rift Valley salt mix, at perhaps 1/4 to 1/2 the stated dose. Tweak the proportions a little if you need to: the Epsom salt raises the general hardness, while the sodium bicarbonate raises the carbonate hardness and therefore the pH. The marine salt mix adds a little of both, plus some other minerals of importance to your fish. Use your test kits, and once you get the hardness and pH you want, make a note of what proportions of each you used, and bingo, you'll have very cheap, very effective buffering chemicals.
For decoration I was hoping to use the dead rock (coral) which is available from my LFS. Will using this rock in the fresh water system as well as the above conditioner effectively buffer the water?
<Yes it can, to a degree, but I'd recommend against it. For one thing, using coral this way is unpredictable, and the rate at which it adjusts the pH will vary with time. The more algae and bacteria on the rock, the less effectively it can dissolve. Plus, it has a time-delayed effect on new water you add, so there will always be water chemistry variations when you do water changes.>
I'm hoping that if the pH tries to drop the decorative rock will buffer the water to prevent any drastic fluctuation.
<Yes and no.>
Is this a realistic expectation?
<Not really. If you need hard water, it's much better to incorporate a small bag of crushed coral in the canister filter, adjusting the amount up or down as required. It's very difficult to say how much you need.>
I don't really want to mix RO and tap water as even from a brand new filter Nitrate is already 10.
<For most community fish, this really isn't an issue. Provided nitrate is less than 50, you're fine, and below 20 will suit "sensitive" fish like dwarf cichlids.>
The only information I have found regarding using coral as a fresh water buffer on the net and various other sources is that it may make the water slightly cloudy?
<Can do, but that's purely the effect of silt on coral sand/rubble that wasn't cleaned. On the other hand, varying water chemistry favours diatom blooms.>
Water changes will be 25 liters/5% a week with RO and added conditioner. I was hoping changing this small amount would not effect the tank pH too much and give the coral time to buffer the added water? After previous advice you have provided we were looking at keeping Gourami's and Rainbows.
<Indeed, and neither of these needs particularly soft water; most rainbows actually want moderately hard, around neutral water. Hardy gouramis -- Moonlights, Pearls, Three-spots, Thick-lipped, and Banded -- will be fine either way. As ever, avoid Dwarf and Honey gouramis.>
Thanks in advance and best regards
<Cheers, Neale.> 
Re: Buffering RO with decor.
Hi Neale,
Thanks again for your fantastic advice. The RO filter is a good quality 3 stage and I have had similar (actually worse) results using another RO filter when I was considering making artificial sea water for my marine system.
<I see.>
Is 10ppm really too high?
<10 ppm what? Nitrate? Calcium carbonate? Calcium oxide? Just to set your mind at ease, in all three cases the answer would be "not too high at all" and in fact in terms of calcium oxide/carbonate very low indeed.>
pH of the RO water is 7 by the way.
<Rainbowfish will do fine at this, provided any drift is upwards, not down; on the whole, the common Rainbowfish species dislike acidic water, though there's some variation.>
Unfortunately I now have a slight problem... The original email you didn't receive was written a week ago and the one you received today was mainly a cut and paste. Unfortunately I have already progressed (in this case not a good thing) and added the Coral.
No problem just remove it right?
<None. The rate at which it dissolves is very slow -- it's limestone after all -- and the impact a single chunk of coral has on aquarium chemistry is relatively small. Naturally, the more acidic the water, the faster the lime dissolves. But I can't imagine this being a big deal.>
Well the condensation lids and frame work have now been fitted around the tank very permanently. The problem is the biggest piece is too big to remove without hacking it to pieces.
<Oh dear.>
This is possible but I'm worried about scratching the tank in the process.
<Yes, certainly can happen, though limestone is softer than glass, and less likely to scratch glass than, say, silica sand.>
Could I just use the Epsom salts to increase the general hardness and use less Sodium Bicarbonate and marine salt to try and get the balance?
<Certainly. But bear in mind that with the coral in there, the pH is unlikely do drop below pH 7.5, since when it does become acidic, the coral will react at a rate proportional to the surface area of coral exposed to the water. If you're keeping hard water fish, then that's fine.
Rainbowfish, livebearers, wrestling halfbeaks, etc. will all thrive in such conditions. Hardy gouramis should tolerate such conditions, too.>
The pH is currently at 7.8 but the tank is still at the Nitrite stage so I don't know if this result is meaningful yet. I will take a hardness test once I locate my test kit which has temporarily gone MIA. I will break and remove the Coral if necessary. I wish I'd been more patient but had almost given up on getting a reply :-(
<Ah, well, these things happen. Do try and understand what coral does, and what the limits are. Surface area dictates dissolution rate, which is why pulverised coral rubble works better than big chunks. pH further determines dissolution rate, and above about pH 8, dissolution rate is practically nil, while acidification below 7.5 will speed up dissolution, cancelling out any attempts to lower the pH -- probably not an issue here, but worth understanding should you decide to keep soft water fish such as tetras.
Over time algae and bacteria cover coral and coral rubble, acting like a layer of insulation, slowing down dissolution further. If the coral or coral rubble aren't cleaned, there's the potential for acidification of the aquarium to proceed faster than the coral dissolves, leading to pH drops.
This can, does happen in neglected hard water tanks where you can find below-6 pH levels despite the use of coral or limestone.>
Many thanks
<Cheers, Neale.>
Re: Buffering RO with decor.
Thanks Neale
<Hello Ben,>
I will endeavor to keep the tank and Coral spotlessly clean and avoid soft water fish. The wrestling halfbeaks look very interesting and are not something I've come across before.
<They are indeed very interesting, and among my personal favourites.
I will promptly and happily make a donation to Wet web media although I believe the information you guys give on this site is ultimately priceless.
<Nice of you to say so.>
I have received great guidance on several occasions now and only wish I could return the favor.
Kindest regards
<Glad to help! Cheers, Neale.>

Ro water in freshwater system  4/23/10
Hello. I have a question (or two) about using RO water in a freshwater system. After moving to a house which is on well water, I have been having trouble getting my water and my soft water fish (killies, tetras, etc)
reconciled. We have incredibly alkaline water, and keeping the pH in an acceptably low range has become a chore. I have used distilled water mixed with tap water, and have tried adding buffers to the mix. I am getting ready to move my fish into a 100g, and am thinking that buying enough distilled water will get very expensive. I have instead decided to get an RO unit. My question is this: Is it better to use 100% RO water and add the necessary trace elements to it, like in a marine system? Or should I mix RO and tap water?
<It's six of one, half a dozen of the other. In theory, RO water is the best choice because it's a blank canvas, and if you add Discus salts or similar, you'll get a precise set of water chemistry with no nitrate in the
water either. Mixing tap water with RO water is less precise, and reduces rather than eliminates any nitrate in your tap water supply. But this approach is also cheaper and easier. In my case, I use rainwater rather
than RO water, and just do one bucket of RO water for every one bucket of rainwater, and the resulting medium hard, slightly basic water is ideal for a very wide range of fish species. No mess, no fuss. But because the mixture has half the nitrate of tap water rather than none at all, it is less suitable for nitrate-sensitive fish, and it still isn't acidic water, so by itself not ideal for species that absolutely must be kept in acidic conditions. Do understand though that most tetras, killifish and other South American, West African and Southeast Asian fish are perfectly healthy in moderately hard water, around 10 degrees dH. This may not be soft enough to breed them, but it's fine for maintenance. Plus, truly soft water has some shortcomings, not least of which are pH instability and the fact biological filtration occurs less quickly below pH 7 and hardly at all below pH 6.>
If the 100% RO water is the better choice, what do I need to add? Is one of the various blackwater or Amazon additives like Kent Discus Essential or Amazon Rain sufficient?
<If you start with just RO or for that matter rainwater, they yes, you need to add Discus salts. Alternatively, a very low dosage of Rift Valley salt mix might work, perhaps 10-20% the dosage, but you'd want to play around a bit and tweak the proportions of the three constituents of that mix until you got what you want. For most soft water fish, you're aiming for about 5 degrees dH, pH 6.5.>
Should I add one of those either way? Ok, it was more than one or two questions, but I just kept thinking of them as I typed. Thank you so much for your help.
Kim H
<Do read here:
Cheers, Neale.>

RO water/water softener... FW  1-11-2008 You helped me about a month ago with snails. The catfish food worked great! Still have a few stubborn snails though. But, I wanted to ask about reverse osmosis water. My tap water is very acidic (measures anywhere between 4.2-5.3) and extremely hard. <Very odd. Are you sure? Typically hardness, at least carbonate hardness, works against acidity. It's pretty normal for municipal water to be hard and basic (alkaline), so I'm assuming your water is something different, maybe well water?> I've bought 2 types of hardness kits, and the readings are practically off the chart. I bought a Pur filter and use that with the freshwater fish, but every time I change the water I lose a fish or two. <Rule number 1: choose fish that like your water chemistry, rather than force your fish to adapt to your water chemistry. Rule number 2: if you have funky water (which you do) treat the water first to make it either [a] soft/acid or [b] hard/alkaline. Those are the options preferred by most fish.> (I have pearl Gouramis, Rasboras, gobies, ghost shrimp, and neon tetras) It's the shrimps and Neons that have a hard time through the water changes. I've read that peat moss softens the water. <True, but oh so slowly and very unpredictably.> How long does that take? <Depends on the peat, how much water, how hard the water is, temperature, etc., etc. Usually not practical.> I usually fill the bucket up (I change 5% water/55G tank- less deaths) weekly and let it age for a couple of days. I use dechlorinate chemicals, so I know that's not the problem. I even used Prime, thinking maybe nitrates. If I put peat moss in the bucket for 2 days, would that be long enough to soften the water? Would it also help with pH? <Nah... forget it. Too much work. My recommendation here would be to work to raise the pH, which is much much easier to do than lower the hardness. All you need to do is filter the water through crushed coral for a couple days. Or better yet, add a mix of Epsom salt, marine salt mix, and bicarb, thus: Per 5 gallons/20 litres * 1 teaspoon baking soda (sodium bicarbonate) * 1 tablespoon Epsom salt (magnesium sulfate) * 1 teaspoon marine salt mix (sodium chloride + trace elements) This will create something roughly equivalent to Lake Tanganyika. Mix plain tap water with this stuff, perhaps at a ratio of 50:50 to start with, until you get something that comes out as hard and basic (pH 7.5). The elevated carbonate hardness (measured in degrees KH) will act against acidity. Although hardly ideal for South American fish, this will work great for fish that like hard water: rainbows, livebearers, Goldfish, African cichlids, etc. There are various barbs and tetras that do well in hard water, too. A bit of research will reveal these. The x-ray tetra is one of the best.> If not, I saw RO units at Lowe's the other day. Are these the same as the RO units in fish catalogs? I read that RO puts the pH around 7.0, but would the water become more acidic? <An RO unit doesn't change the pH as such, but it removes the buffering capacity of water, so that it becomes very prone to pH changes. Because tanks tend towards acidification, very soft water usually becomes acidic very quickly. See here: http://www.wetwebmedia.com/FWSubWebIndex/fwsoftness.htm > I've read that when you add chemicals to change the pH, it doesn't work for very long and the pH goes back to what it was before you treated it. <Changing the pH without changing the hardness (specifically: buffering capacity) is indeed a waste of time, and not that kind to the fish, either.> If the RO water is better in the long run, there is a carbon filter (this is the Lowe's model I was reading), would I still need carbon filters in the fish tank? <No-one really needs carbon in a freshwater aquarium. It's largely a gimmick/holdover from the past. Haven't used them in 20 years.> The last time I changed the water I used a gallon of distilled water mixed with 5 gallons Pur filter water and no deaths. But, I use distilled water for the saltwater tank and going this route (both tanks with distilled water) would become a little more expensive. Would RO water be the same as distilled? <Not quite, but admittedly much more cost effective. Do read here: http://www.wetwebmedia.com/ca/volume_2/cav2i4/RO_systems/reverse_osmosis.htm > Hope you understood all this, I'm still confused about how ask all this, Thanks, Robin <Hope this helps, Neale.>

Betta and ADF, sys., RO water use,   11/25/2007 Hello All, Thanks in advance for the advice. Normally I am asking marine questions, but I have a few probably very silly questions about a Betta tank. I have a six week old, cycled, 3 gallon Eclipse tank with a male Betta and one African Dwarf Frog. Parameters are Ammonia/Nitrite: 0, Nitrate: less than 20, pH: 6.0, and nearly zero on DH and GH. The tank has live plants and a one inch gravel bottom. So, the first question: I use RO/DI water instead of using a conditioner on tap water. Is this okay or are my DH and GH readings too low from filtering out too much? <Always mix some tap water with the RO water; by itself, RO water isn't acceptable for most fish. Aim for between 5-10 degrees dH. For a Betta, there's absolutely no advantage to using RO water anyway, since these fish are very adaptable and provided extremes are avoided couldn't care less about water chemistry. Moderate hardness and neutral pH is probably the ideal.> I had assumed the RO/DI was better, plus it is convenient since we have the unit set up for the salt water tank, but now I am wondering. <Very soft water causes problems with acidification and lack of stability.> Second question: When I come into work in the morning, the tank is usually around 77 degrees F. With the light on during the day, the temperature usually creeps up to about 80 or 81. Is this too much fluctuation over a 24 hour period? <It's fine for a Betta. Certainly "within the margin of error" for what a wild Betta would be exposed to.> Should I try and bump the heater up to keep is closer to 80 at night? <No point if the fish is otherwise fine.> Of course then it would still fluctuate up to 83 or 84 in the day then. Third question: I have read your FAQs on ADF, but was still unsure about a few things. I have only one, are they social and should be kept in multiples? <I think they are better termed "sociable" rather than "social". They don't form schools as such, but provided they aren't overcrowded you can keep several in a tank and not have problems. A gallon of water per frog is often recommended, and seems about right.> I feed about 2 bloodworms (still need to get other "meaty" stuff, frog is new) every 2 to 4 days. Should this be sufficient? <Depends on the size of the frog, the quality of the bloodworms being used, water temperature, and so on. Provided the belly is gently convex but not bulging, you're fine. I'd be feeding this half a dozen bloodworms every day and seeing how things go from there. If they get portly on this, skip a day or two per week. If they look thin, I'd feed slightly more food, perhaps across two meals per day. There's no hard-and-fast rule to how much to feed any animal; to some extent you need to observe and react accordingly. Provided you don't give the frogs so much they look like bowling balls with legs, then the issue isn't overfeeding per se, but water quality.> I know it is hard to say without seeing the frog, but does that sound like a reasonable amount of food? <A bit too little, too me.> Any other advice is always appreciated! Thanks! Michele <Cheers, Neale.>

Discus setup and R.O.; Tank Mates For Discus   8/26/07 Hello crew, Have put up posts on the public forums but no reply as yet and tbh would appreciate a fairly quick reply if possible. Since the volume output production of my R.O. unit is slow, a trickle, it is best at the moment for me to perform one 15 litre w/c per day which over the course of a week equals a 50% w/c on both tanks. This equates to a 7 - 8 % w/c each day. Is this low level change ok to do or are the benefits minimal? < This depends on where you water chemistry is now and where you want it to be. If you are trying to lower the pH then it probably won't do much good. If you are trying to lower to total dissolved solids then you should be fine.> I'm getting two huge tubs soon so I can just turn it on and walk away for a couple or few hours without having to tend to it all the time. Last of all, my father and I have decided to take the direction of our main display tank to a Discus setup. I have read Bob Fenner's article called "The cichlid fishes called Discus". I'm trying to find out if the temps for them would be too high for Syno cats, eupterus and nigriventris. Mr. Fenner gives an example of suitable fish companions for Discus, was wondering if there was a particular exact source (or your recommendation) for a few more species. I don't think I'll be able to get the pH low enough for cardinals. We appreciate that these fish need extra special care and fully intend to create as perfect and suitable environment for them as possible, low lighting, correct plants, right GH and KH etc. Many thanks team. Steve. < The Synodontis cats get big and are big eaters. I'm afraid that they would bully the discus away at feeding time. Look for tankmates that can tolerate the same water conditions and will leave the discus as the dominant species in the tank.-Chuck>

Converting from r/o water to tap water in my discus aquarium-BIG pH difference! -- 07/03/07 Hi guys. First, thank to all of you who have so graciously answered my previous questions. I have learned a LOT from reading on this website and from the experts here. <Welcome> I am very interested in converting from r/o water to tap water in my 55 gal discus aquarium. They need minerals, etc that they have not been getting from the r/o water, <Mmm, good... Yes... some... all depends on a few factors... What your source water is "made of", how "wild" to cultured your Discus are...> and I need to improve my water change method. Pouring r/o water into the tank by the gallon is really old now after 3 years in this hobby! I have had my discus for a year now, and all seem to be happy and healthy. For my first mixed water change, I used 3 gal treated tap water plus 20 gal r/o in my 55 gal aquarium. I treated the tap water with Seachem Prime and aerated it in a bucket overnight using an airstone that I already have. I tested the water before using it. Nitrate and nitrite were zero. Ammonia was also zero, but I understand that the Prime could have affected that test. Here is what concerned me about the tap water: the pH was high-it read as high as my test kit measures, 8.8. <Wow! Liquid rock!> The pH in my tank is somewhere between 5 and 6, I believe. I do not know WHAT the pH actually is. My SMS122 controller seems to have malfunctioned. Even after replacing the probe, the reading it gives is too low for the fish to be surviving, much less be doing well, according to Neale (thank you Neale for the information). After doing the water change this weekend, the reading on the controller went from 4.1 to 7.0. Hard to believe that 3 gal of tap water plus 20 gal r/o could move the pH like that. What do you think? <I think your previous water/system had almost no alkaline content... was likely very poorly (and dangerously) buffered... and that the change was in the right direction> Any recommendations or advice will be very gratefully received! I do not want to stress my fish during the transition. If you can recommend how to proceed from here, I would really appreciate it. What should I do about the pH and how slowly should I mix in the treated tap water? <I would continue with the changes in about the proportion you're doing them, and observe your Symphysodon carefully> I have read that treating the tap water with peat would soften it and lower the pH. I tried this early in my discus fishkeeping, and lost one small little guy the morning after adding a small amount of peat to the aquarium (may not have been related to the peat I guess). What I used was Scotts Sphagnum peat moss. The bag states 100% peat moss. I see no mention of any additives. <Mmm... don't always state... better to either buy "aquarium use" material or even just an "extract" product really...> My fish are great little buddies who have survived my novice care, equipment failures, and my mistakes for a year now! I want to keep it that way! Thanks again for any help. <I suspect the mixed tap and RO will serve you and your fishes well here. I would not be overly concerned with the resultant system pH if it is about neutral/sevenish. Bob Fenner>

R/O Water and Discus 6/30/07 Hi crew! <Hi, Pufferpunk here> I have used only r/o water in my freshwater discus tank for a year now. <Not necessary. Most discus nowadays are tank bred, in regular tap water. I do 90% weekly water changes with tap water, conditioned with Seachem's Prime.> Although the fish appear to be fine, I realize that I have failed to add back in minerals and trace elements that the fish need. My choices appear to be either reconstitute the r/o water or convert to tap water and treat it prior to adding it to the aquarium. Therefore, I am interested in converting to tap water, very slowly of course. I will treat my tap water with Seachem Prime, <Aha! Took the words right out of my mouth!> as is recommended on this site and aerate it in a storage container for a couple of days using a powerhead. <Not necessary. I just drain, adjust the temp & fill, after adding Prime to the tank.> My question is this: how gradually would you recommend adding in the treated tap water? A guy at the LFS recommended 10-15% treated tap water to begin with, then increase tap water about that much w/each water change. In addition to increasing the TDS, <TDS has no effect on FW/SW fish, unless your tap water contains ammonia, nitrites or nitrates.><<What? No! RMF>> it should also effect the pH in the tank, which is less than 6 and has been for a while. I do not know exactly what the pH is because my SMS122 pH controller appears to have failed and my freshwater test kit only measures down to pH 6. If I do weekly water changes of approx 40% like I am currently doing, would this result in too much change too fast? Any advice will be gratefully received!! <I would start with 25% every other day for a week & then do at least 75% weekly after that.> I have purchased a Rubbermaid Brute 44gal trash can with top, and one of those cool dollies to roll it to my tank! I plan to pump the treated water into the tank using the powerhead. I am very excited about improving my water change method and giving my fish better water! <Make your improvements even easier by just using a Python to drain & fill right from the tap. Can't be much easier than that.> Thanks for all the great advice on this site!!! You guys are the best! <Hey, thanks a lot! We try...> P.S. Do you have any recommendations for the powerhead? I will only need to pump from the storage container into the aquarium, so I guess the head would be less than 5 feet. I plan to connect pvc pipe with a couple of elbows to the end of my hose so I can just hang it on the lip of the tank and let it fill. <Keep it simple! (Unless you are planning a reef tank in the future.)> Thanks again and I hope you all have a great Independence Day! <Happy 4th to you too! ~PP>

Bacterial Hemorrhagic Septicemia / fin and tail rot  6/30/07 Hello, <Hi there> I have a 16 year old Silver Dollar that has the following conditions. Left pectoral fin is gone; the flap is there and flaps like crazy, but there is no fin attached. <Mmmm, might grow back if not too far gone...> Both pelvic fins are completely gone. The caudal fin is badly frayed (3 weeks ago was almost completely gone) and is strangely red at the base close to the fish body. <Something amiss here...> History; up until 6 weeks or so ago, I had the silver dollar in the tank with a Pacu. <Ohhh> The pacu was huge and out sized the dollar by ten times at least. One day I noticed that the silver dollar was missing most of its caudal fin and what was there was badly frayed. The pelvic fins were gone as well as was the pectoral. I assumed it was fin and tail rot and treated the tank with Mardel Maracyn Two. The caudal fin began to get better for about a week then went to worse again. <... stress, bullying...> I then thought that it was the pacu. Although the pacu never picked on the dollar in my presence I thought it was happening when I was not around. I wanted to get rid of the pacu any way since it was so big and messy to take care of. I found a home for the pacu at a LFS adoption tank and that left my dollar to her self. The caudal fin healed from almost nothing to about one-half but then quit and will not heal further. The other fins have not changed at all. I am patient and though that in time all would be well again so went out and bought 3 more silver dollars to keep the old one company. Before getting the new dollars the old one ate well, but now the feeding frenzy and competition is causing the old dollar to swim faster to get her share, but with out the control of all her rudders she cannot aim correctly at the food and misses it. <Provide more bulky food items... greenery that the impaired one can eat easily... Like blanched zucchini> Also, she cannot maneuver well enough to keep up with the other dollars who are younger and smaller. This is causing me to revisit medication or some form of treatment before the dollar winds up dieing. <... Medication not advised here> My tank is 75 gallon, Ph - 6.8, nitrite - 0, ammonia - 0, Nitrate 20-40, GH 3d, KH <1d, total dissolved solids 300ppm, RO water conditioned with Kent RO right, <I'd use less, let the TDS hover around 100 ppm> Ph buffered with Kent Ph 6 and 7 (phosphates), and the temp is 25.5c. My 1st question is this- I read that the redness near the base of the fins could be Bacterial Hemorrhagic Septicemia. Does it sound like it to you? <This... is a condition... Need to seek out, address root cause/s... the trauma, "dirtiness" from the Colossoma... Takes time to heal...> 2nd, Can the pectoral and pelvic fins come back if I treat the fish correctly, or are they gone for good? <Can regenerate> 3rd, what/how would you recommend treating the condition(s) with and should the treatment be carried out in a separate tank, or is the condition contagious, requiring that the entire tank be treated. Many thanks! Scott S <I would try the change to foods with more bulk, lowering the TDS, soaking the food/s in a vitamin and HUFA mix like Selcon to boost this animal's immune system... Bob Fenner> Re: Bacterial Hemorrhagic Septicemia / fin and tail rot   6/30/07 Hi Bob, Thanks for the quick reply. <Welcome!> I'll take your advice and not medicate. How do I lower the TDS? <Mmm, either start with "cleaner" water or not add to it...> I add chemicals when I do water changes as follows. To 15 gal I add 1.5 tsp Kent RO Right, <Leave most of this out... this should do it> 1 tsp Kent Ph Precise 6.0, 0.5 tsp Ph Precise 7.0, and 15ml Tetra Black Water Extract. That brings my TDS in the new water to 235. Still even then my GH is very low, between 2-3 dH, and the KH is so low I cannot measure it. Would you add different quantities/products? Thanks again, SL <Try cutting back on the RO product... try a level teaspoon of baking soda (Sodium bicarbonate) instead...>

Re: Bacterial Hemorrhagic Septicemia / fin and tail rot, Silver dollar...  6/30/07 Hi Bob, You must have forgotten that I am using RO water, or I doubt that you would recommend that I only add 1 tsp of baking soda to 15 gal of it. <I did not forget anything...> On the label of the RO Right, it recommends 1 tsp per 10 gal for soft water. That is what I am currently adding. Also, on the Ph Precise I am following the label as well. Since my fish has out-lived my dog, I must be doing something right with respect to water chemistry and husbandry. <... what is your point?> My quandary is in treating an old fish which has lost much of its finnage, and over an 8 week period has not shown much improvement despite a great deal of effort. Your suggestion of more bulky food was a good one. The silver dollar seems to really like green beans, and since none of the other dollars pay any attention to them, the wounded one has them to herself and once again has a full belly. Also, I have taken your advice on supplementing vitamins. I have no experience with mixing food, so I am adding freshwater essentials to the water to add vitamins. Hope this works in lieu of. Thanks for your help, SL <Please... just use the indices, search tool. RMF>

Re: Bacterial Hemorrhagic Septicemia / fin and tail rot -- 07/01/07 Bob, <SSL> What is my point you ask? Most of what I do with respect to maintaining my fish tank is based on information gleaned from posts on your web site and from your direct responses to my previous questions over the past 2 years. I.e., RO water instead of tap, frequent water changes, softer water, discontinuing fish-slime additives, etc. <I am in agreement with all of this> Then, in this most recent volley of correspondence you suggest that I go to pure RO water without any additive other than baking soda <Sorry for the lack of clarity... I would try decreasing the RO Right product by half ml.s per time/maintenance interval, and in addition, add the level tsp. of bicarb> which would leave my tank with out any major or minor elements, no GH, and enough alkalinity to bring my Ph back up to 8.0. Why would you suggest this? It makes no sense to me in light of the other comments and suggestion on your site. SL <Do try this in a separate container... and measure the resultant chemistry... a day later. B>

Are the water fountains that we drink out of a good source of ro water?   5/22/07 <Would depend on the water fountain. Most aren't using RO water, as far as I know. Here in the UK most either use regular tap water or draw from giant bottles of mineral water. Regular tap water is safe for fish once dechlorinated, and mineral water is also safe but obviously too expensive to use in a fish tank! If in doubt, as the manufacturer of the system concerned. Unless explicitly declared safe for fish, don't use it in a fish tank.> Also, the coffee makers at gas stations have got water and I have sometimes noticed a filtration system of some sort would this be ro? <Probably not.> Thanks Joe <Cheers, Neale>

RO vs. Distilled 2/02/07   2/6/07 We have a 37 gallon, and we're trying to lower the hardness to 7 or so for the loaches and tetras.  When we change the water, we were doing 2 gallons of RO and 2 gallons of our filtered tap water so we could slowly change it down.  Then once we got the hardness we wanted in the tank, we would premix our water to that hardness and add it. <Good plan>   We thought this would be the simplest way.  We couldn't find any water test kits for hardness, so we had to order it online.  We tested both the aquarium water and the RO water the day we received the test and then switched over to distilled after finding the RO so hard. <Something is amiss here... the RO should not be "hard"> We thought doing it this way would be more gradual then doing a whatever amount change and switching it soft so soon (since this also comes with a ph drop).  Is there a better way?   <Yes... checking the RO, or taking a water sample from it to a dealer who works with such, having them check the make-up, suggest what may need to be done (replacing membrane/s, contactors) to fix it> Also, we have the neons in the tank, the loaches in QT, and the Rummynose tetras aren't bought yet.  The Rummynose are kept in hard water at the LFS.  Would it be better to prepare the QT with the same softness as our aquarium will be and acclimate them to that right off the bat, or would it be better to gradually make their QT water softer? <The latter is better> (They're also kept at a PH of about 8.3, whereas ours is currently 7.2 and hopefully somewhat lower by the time we're done adjusting.)  We acclimate by adding water several times to a floating bag over about an hour to and hour and a half.    Thanks again for your time and everything you add to the hobby. Celeste <Thank you for your carefully crafted correspondence. Do have your Reverse Osmosis device be checked. Bob Fenner> Putting RO water in a freshwater tank  12/23/06 <Hey Keith, JustinN with you today.> First of all, awesome website, you have taught me so much and I have told sooooo many people about your site and they love it also. <Thanks for the kind words, is a collaborative effort.> I have an RO system at my house for my saltwater tank.   <Ok> I also have a 40 gallon freshwater tank with some live plants, baby red ear sliders (5 inches), a few tiny tetra's and a few tiny gold fish, and a freshwater crab. <Fish and turtles aren't really compatible, nor are goldfish (cold water) and tetras (warm water), but ok..> I have read that you should not put RO water in freshwater tanks, then some articles saying you should? <The idea is that you should not use untreated RO water, as there is no mineral content. There are several buffering powders specifically for freshwater tanks that can achieve this. Another method, which I personally employ, is to use 2/3 RO waste water to 1/3 RO water for my freshwater tanks. The RO waste is dechlorinated already, and it cuts down on the wasted water!> The tank has been running great with tap water.  The only thing I do to the tap water is add dechlorinator (although sometimes I forget) <Forgetting is not a good thing here.> Anyway, should I use RO water from here on out?  Should I buffer it?  Any suggestions? <I would suggest using the method noted above combing RO waste water with RO water for water changes from here on out. It will alleviate any worry about needing dechlorinator.> Thanks! <Anytime! -JustinN> Have a great Christmas!!!

RO/DI water vs. mechanical filtration   11/15/06 Hey Jorie, it's Roni again! <Hello again! I tried to write you back last night, but my computer was acting up...> I was doing some research on cycling a tank.  With my new 55 Gal, I already have a hang on the back type filter (I am at work right now and couldn't tell you exactly what kind.) <That's OK...brand doesn't matter too much, so long as the filter is rated for *at least* 55 gallons of H20...> I am going to give it a try before I invest $200 in a RO/DI filter. <Hmmm, I think you are confusing two concepts here - establishing the nitrogen cycle in a new tank and mechanical filtration are two separate, distinct issues.  All tanks need to be cycled, even those that use purified (RO/DI) water.  Read here: http://www.wetwebmedia.com/FWSubWebIndex/fwestcycling.htm .  The filter is the mechanical means by which sediments are trapped in the filter media; the filter media (e.g., carbon) is what will eventually be "colonized" by the beneficial bacteria to establish the nitrogen cycle.  Read here: http://www.wetwebmedia.com/FWSubWebIndex/fwfiltration.htm > (Probably not what you would suggest, but $200.00 is a little much for me financially right now). I was reading in a forum on www.thetropicaltank.com that you can hang your new filter on an already established tank for about a month to get the cycle going.  Can this be done in my situation?  Hanging a 55 Gal filter on a 10 gal tank?  Won't the water move too fast for the fish I have in the tank already? Just would like your opinion on this. <It is true that you can "seed" a new tank with old filter media, and/or water and gravel from an established aquarium.  I think what you read about was someone taking media from an established tank to help speed along the cycle in the new tank.  You can accomplish this by allowing bio-balls to establish in the old 10 gal., or you could even use a media bag filled with carbon, or the like, in the old filter for a few weeks, then transfer the media to the new tank.  It isn't the actual filtration hardware that will transfer the beneficial bacteria necessary to establish the cycle, but rather the media (i.e., whatever you are using inside the filter to help keep the water clean).  All of this will only help speed the process up, but won't eliminate the need for "cycling" altogether.  Do read the latter article I linked you to for details on cycling.  Also, as I think I previously recommend, check out David E. Boruchowitz's book entitled "A Simple Guide to Freshwater Aquariums" for a very simple, well-written chapter on cycling. The RO/DI unit simply makes pure water for the aquarium to use; it will still need to be cycled.  On that note, a cheaper alternative to the expensive RO/DI unit is a product called "Tap Water Filter" by Aquarium Pharmaceuticals...I believe it's around $35 - this is simply a de-ionizing unit, without the reverse osmosis.  The reason people use these types of units is that their source (tap) water contains "undesirables" such as ammonia, phosphates, etc. Hope I've clarified - let me know if you are still confused!> Thanks Jorie Roni <You're welcome. Best regards, Jorie>

Last question on RO water for FW   10/2/06 Hello <Hi Steve> This is my last question on RO water. <OK, well this is the first one I've seen - you've got Jorie today...since there was no forwarded message, I wasn't sure who on the crew had previously helped you, so I thought I'd just give it a shot! Hope you don't mind...> After my water is purified could I add a product such as Kent's Discus Essential and Tetra's Blackwater Extract to add to the purified water what the fish need instead of adding an RO Right supplement. I ask this because a friend of mine can works at a Petco and can get me these product for very cheap. The PetCo he works at doesn't carry any RO additives, so I would have to pay full price to get them. <Unfortunately, you are talking about two very different types of products.  I do understand wanting to save money whenever possible, but if you are using RO (or RO/DI) water, it is essential to add back essential elements and trace minerals; even a quick scan of websites such as this [ http://www.petstore.com/ps_ViewItem-SearchStr--action-view-idProduct-KM5691-idCategory-FWASDS-category-Kent_Marine_Discus_Essential_8_oz._Freshwater_Aquarium_Supples_Additives___Conditioners_Discus_Supplements-vendor-Kent_Marine.html ] specifically state that you must use a product specifically designed as a RO or RO/DI additive before using the other.  I do not have any personal experience w/ Kent's RO Right, but instead use the combination of Aquarium Pharmaceutical's Electro-Right and pH Adjust after making my RO/DI water.  I know that some larger chain stores carry these two products, and they can be found right next to the "Tap Water Filter" made by Aquarium Pharmaceuticals, usually.  Ask your friend specifically about these two...each one shouldn't be more than $6.00, and a bottle will last you a long, long time (460 gal. or so).  Here's where I order from: http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=4492&Ntt=electro%20right&Ntk=All&Ntx=mode+matchallpartial&Np=1&pc=1&N=0&Nty=1 Sorry about all the questions but I have absolutely no experience with RO systems... <No worries - we all learn through the question and answer process!> ...and I am only 17, so my funds are a little low... <Well, I'm nearly twice your age and I still understand that predicament!> , and if it is possible to use these products instead of the "RO Right" products, it would save me a lot of money that I could invest else where in the tank. <I understand, but you just can't do it without sacrificing the health of everyone in your tank.  Honestly, I make about 10-15 gal. of RO/DI for freshwater use weekly, and I've been on the same bottles of Electro-Right and pH Adjust for months now. Best of luck, Jorie> --Sbatiste RO remineralization   10/2/06 Hello everyone I'm back with another question regarding ro water. I want to keep soft water species such as angelfish. So I bought an ro unit to soften my water and lower my ph. <Good. A useful, appropriate tool> Now from what I understand you have to remineralise the water, but don't the product that do this such as Kent's RO right add stuff back to the water that makes it hard again, like calcium and magnesium. <Yes... to a variable extent... depending on how much you put in> I searched the forms but couldn't quiet grasp the info. Basically what I'm asking is, after you RO water do I have to add anything to it since I'm keeping soft water species such as angelfish, and if I do have to add anything what should I add, should I add the Kent RO right. <I would add some... use tests... likely Alkalinity... to gauge how much you want/need> Thanks, sorry for the drawn out question but I couldn't understand the information. --Sbatiste <Have recently "split up" the RO FAQs, but most relate to marine issues. Bob Fenner>

RO waste water, RO FW use   8/18/06 Hey crew, I believe I remember a few times that Bob has suggested using RO waste water for water changes in outdoor ponds... <Yes... have done this for many years... only slightly more solute laden than the tap/source water> my question is, is this water safe for a FW community tank that has been using the same source water, dechlorinated, from the beginning? If so, would the waste water have to be treated in any way other than aeration for a few days before use? Thanks, Justin <I would mix in some RO along with the source water (for a source of mineral)... can be aerated, stored ahead of use... but most RO devices remove all sanitizer... and if done "properly"... i.e. only partial changes, not much use in aerating, using immediately. Bob Fenner>

Is An R/O Unit Needed?   7/7/06 Hello WWM, I am thinking of getting an RO or RO/DI unit in the near future and was wondering if I really need one with these Tap water parameters. Here they are: Nitrite <2.0  <<Should be zip... I would NOT drink this water. RMF>> alkalinity 84 ph 7.4 phosphate 17 <<Parts per million? Yikes!!! RMF>> silica 16 Is it necessary to get a filter. If so, do I need RO or RO/DI? Thanks so much for the help Mike < All of this is dependent on what kind of fish/organisms you are planning to keep. If you are keeping a sophisticated reef tank, then you might want to invest in an R/O unit so you have complete control over the minerals in the water. Fresh water fish that require soft water like wild discus would be better off with R/O water. With the water parameters you have given I would think you could keep the vast majority of fish in the hobby.-Chuck>

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