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FAQs on Seawater Salt/Use in Freshwater

Related Articles: Salts (Marine, Table/NaCl, Epsom): Use in Freshwater Aquariums & Ponds by Neale Monks, Choose Your Weapon: Freshwater Fish Disease Treatment Options by Neale Monks, FW Disease Troubleshooting, Freshwater DiseasesNutritional Disease, Ich/White Spot Disease

Related FAQs: Using Salts in Freshwater 1, FW Salt Use 2,
FAQs on: Salt Use for Treating Ich, Salt for Treating PopEye, Salt for Treating Bloat, by type of salt: Table/NaCl, Epsom/MgSO4, Rift Valley Salt Mix, &
Freshwater Medications, Aquarium Maintenance, Ich/White Spot DiseaseAfrican Cichlid Disease 1, Cichlid Disease


To salt or not to salt...    9/1/10
Hey crew!
<Hello Matt,>
I'm starting a brand new 29 gallon tank this week. Been adding bacteria and was told to put in a black molly.
<Why? A very bad first fish for a freshwater aquarium. Quite a good choice for brackish and marine tanks though.>
From what I read on your site (I've read A LOT) that was a good thing for them to suggest.
<See above.>
I'm in the waiting period for the cycle right now and while waiting I'm reading up on the next fish that I'll be purchasing. Reading a lot about freshwater, adding salt or full barack.
<Brackish, not Barack, who if I recall correctly is the President of the United States of America.>
My question is simply what is the best direction to go from here. I'd like a tank with some specific things going on and I'm not sure which tank type would best serve my desires.
<Ah, I see. If you want Mollies, the best approach is to understand their needs, and then at the very least choose companions that will tolerate slightly brackish conditions, should you need to add some salt. Neon tetras would be bad, but Australian Rainbowfish would be good. Corydoras catfish bad, but Brown Hoplo catfish good. Clown loaches bad, Horseface loaches good.
If you aren't wedded to the idea of keeping Mollies, then of course you can choose plain vanilla freshwater fish, though I'd recommend you choose species that appreciate your local water chemistry. If you have hard water, then hard water fish livebearers are good choices; if you have soft water, then tetras are more sensible.
I'd like a school of colorful active fish swimming around, I'd also like a few bottom dwellers (I'd like invertebrates, but keeping the tank clean and healthy is my main focus), and a "show-fish" of some type.
<Indeed. Read above.>
A cool looking one that gets up to 4 or 5", but obviously not too big for my tank. I'm not going to jump into real plants yet. I'm not interested in breeding or anything yet so I'd either like the bottom dwellers or large fish to take care of any fry, or not mix males and females.
<If you keep Mollies, Glassfish (good in freshwater or brackish water) or Knight Gobies (brackish water only) will eat any fry produced.>
I've read compatibility charts after compatibility charts but it's difficult to put together names of fish with how they look all while remembering which are freshwater and which are barack. I'm learning that I can't ask the people at our pet store and trust their answers!
<It's really not that hard. Start by establishing your water chemistry.
Soft water, hard water, or if you add marine salt mix, brackish water. Then decide the water temperature. Neons and Platies for example need cooler water than Angelfish or Guppies. By the time you've reviewed these factors, you can then go through your aquarium book and choose the species you want to keep. Let's say you have hard freshwater but don't want to add marine salt mix. So you won't want to buy Mollies. You further decide to keep the tank relatively cool, 24 C/75 F. Good choices for such a tank include Platies, Swordtails, Zebra Danios, Peppered and Bronze Corydoras, X-ray
Tetras, Blind Cave Tetras, Bristlenose Catfish, Australian Rainbowfish and Florida Flagfish.>
<Cheers, Neale.>
Re: To salt or not to salt...   9/4/10

Thank you very much for the information!
<Happy to help.>
Read the articles and did the research on my water. Chose to go pure freshwater.
The black molly served it's purpose in cycling my tank, 0 ammonia, 0 nitrites, 10 nitrates but since I decided to go freshwater I returned him to the store. Also picked up some test kits and found out that my water was soft and had decent pH (7.4).
I decided to go with a final 29g tank setup of 2 angelfish, 5 swordtails (1m, 4f), and 6 Cory cats.
<Not a perfect set of animals. Corydoras and Swordtails prefer quite cool water and quite strong water currents; Angelfish prefer warm water and gentle water currents. You can keep them together, but you will need to be careful.>
Should I consider trying to keep my pH lower with each water change or just leave it stable?
<Leave it where it is. If you think pH is important, you haven't understood what you've read! pH is remarkably unimportant, and provided it's around 7, it's fine, whether slightly above or slightly below. Hardness is far more important.>
I'm currently going with 78 degrees, good?
<Not for Corydoras or Swordtails, both of which do best between 72-75 F/22-24 C. The exception among Corydoras is Corydoras sterbai, which will do well in the water Angelfish enjoy. If you can find them, Brochis splendens is superficially similar to Corydoras aeneus but unlike Corydoras aeneus it is happy in deep, warm water like that Angelfish enjoy. Because your water is soft, I'd skip Swordtails altogether, and instead keep something like Harlequin Rasboras or the very hardy X-ray Tetras, schooling fish that are happy in warm, soft water and don't nip fins. Avoid Neons and Danios -- these also like cool water. Barbs can be okay, but some species, like Tiger Barbs, are nippy, and will harass Angels. Do also remember adult Angels are predatory, and small fish like Neons and male Guppies are food as far as they're concerned.>
I picked up my angelfish first, will add the others slowly. The angelfish that I picked up are quite small. Slightly over 1".
<Very, very delicate at this size. Would not recommend buying them this small.>
The filter I'm using filters 200 gallons per hour. Are the currents created by my filter (and 2 airstones maybe?) causing my fish to move quickly from cover to cover instead of swimming around?
<Perhaps. Angelfish you buy in shops are hybrids to be sure, but all Angelfish species evolved in sluggish, slow-moving waters moving around sunken wood. They aren't able to swim strongly at all. They're happiest
with water turnover rates of 4-6 times the volume of the tank per hour, i.e., for a 30 gallon aquarium, a filter rated at 120 to 180 gallons per hour. If the water current is strong, use vertical objects like bogwood, rocks, slates and tall plants to create still areas around the tank where the fish can hover. Or else, if your filter has an adjustment dial, turn down the flow rate until the Angels feel more comfortable.>
Possibly staying hidden because of there being no dither fish?
<Perhaps. Certainly, Angels are happiest kept in tanks with dither fish.>
Just needing to stay in the tank for a few more days to get used to it?
Just want to make sure my filter isn't causing these new little guys/girls to be stressed out unnecessarily.
I *think* I've got a good grasp on what's going on because of the info on your site. Just wanting to make sure before problems arise rather than after!
<Very good.>
<Cheers, Neale.> 

salt in freshwater aquariums -- 02/02/10
I'm curious if maintaining a salt level in a freshwater aquarium provides any benefit.
<Usually, none.>
I've read so many different opinions that I thought I ask would about my specific setups.
<Has been discussed to death, I agree. But aquarium health books written by vets and biologists all agree that adding salt to freshwater tanks -- except as a specific treatment to a certain disease -- is usually pointless.>
The first is a 29 gallon with several different goldfish and one albino chocolate Pleco. The second is a 90 gallon community with tiger barbs, panda barbs, green tiger barbs, counterfeit silver dollars, lyre tail mollies, Golden killifish, Siamese algae eaters, Albino dwarf catfish, bristle nose Pleco , African dwarf frogs and several live plants. I've read that many people put as much a one tablespoon per 5 gallons but that seems like a lot.
<Do understand the salinity of normal seawater is about 35 grammes per litre of water. That's about 6 teaspoons or 2 tablespoons of marine salt mix per litre. 5 gallons is about 19 litres, meaning normal seawater contains about 19 x 6 tablespoons = 114 tablespoons of marine salt mix. So your one tablespoon is less than one-hundredth the salinity of normal seawater. A can of soda will contain more salt than that. It's a useless, meaningless amount of salt that won't do anything much.>
I know the live plants don't tolerate much
<Actually, that's not true. Some aquarium plants will tolerate brackish water rather better than many fish!>
but I'd like to know if there is a level that will provide some benefit.
<None. Back in the prehistory of the hobby, adding salt was common. Sodium chloride does detoxify nitrate, and given people did water changes very rarely, this might have been helpful. It's the same reason carbon was used in the past. Like salt, carbon is obsolete now because we have better filters and above all do more water changes. At best, adding salt does nothing, but there are some specific situations where adding salt may cause harm over the long term. See, for example, Malawi Bloat, a syndrome particular to cichlids where constant exposure to salt is believed to be a triggering factor.>
There is so much conflicting info on the net about using salt in freshwater aquariums a good article by you guys would be great, if I missed something that's already posted please forgive me.
<A good idea for an article!><<I'll say! RMF>>
Thank you,
<Cheers, Neale.>

Question RE previous advice given by Neale, H20 chem., FW    5/7/09
I wrote in a week (?) ago or so about water chemistry, and having a high level of sulphur in my well water. I am taking Neale's excellent advice and have decided to keep Mollies for starters once my tank is done cycling. My question now is regarding the salt mix. I'm going to maintain my SG level at 1.005 (hope I got that right), and looked at the salt mix recipe listed on your site (Epsom, baking soda, marine salt). I purchased some Instant Ocean marine salt mix to use, I'm hoping this is the right stuff. Here is the meat of my question: I read on your page about what different ingredients do to PH and hardness, since my water has a very high PH (about 8.4), and is very hard carbonate and bicarbonate, will the salt mix (or some of the individual ingredients that is) raise these even higher?
<The effect will be marginal; while marine salt mix contains some carbonate hardness, carbonate and bicarbonate are buffering in both directions:
besides stopping acidification, they also inhibit pH rises above a certain level too.>
Is there maybe an ingredient I should leave out? Or, since I gathered from reading, "tonic" salt won't do anything to PH would that be a better choice?
<Tonic salt isn't a better choice, though I dare say given your local water conditions, it would work adequately well. In any case, Mollies (and livebearers generally) are happiest in "liquid rock" so what you're doing here isn't going to cause them any hardship.>
Thanks again for you all of your help, and sorry I don't seem to grasp all the concepts easily!
Thanks again!
<Cheers, Neale.>

Fancy Guppies (salinity, calculations thereof) -- 03/02/09 Dear Crew, I am keeping fancy guppies. I have several ten gallon tanks for breeding them in. I am using the Jungle six in one test strips and nitrates are 0-20, nitrites are 0-20, hardness is 150+, chlorine is 0 (well water), KH is 180, and PH is between 7.8 and 8.4. These tanks have been set up a week now. I would like to complete the set up using instant ocean. My question is: Is there a cooking spoon measure that corresponds with the proper amount of salt per gallon and if so, what is it. Thanks for the help. Bill <Hello Bill. There's a reason we don't recommend weight or volume measurements for adding salt: once a salt package is opened, it absorbs water from the air, so over time a given weight or volume of salt actually contains a bit less salt than you think, because some of that measurement is water, not salt. Once you've added some salt to the water, you use a hydrometer to test the salinity via a proxy measurement, density (in this case called specific gravity, or SG for short). For guppies, a low salinity is ample, around SG 1.003 being perfect, and even a bit less being more than adequate. It isn't essential to add salt, but it does help if you live in a soft water or high nitrate area. Now, a salinity of 6 grammes per litre is roughly SG 1.003 at 25 degrees C, and very conveniently, 6 grammes of salt happens to be about the same as one level teaspoon. So if you're prepared to use the metric system, estimating the amount of salt couldn't be easier! Roughly one teaspoon of marine salt mix per litre of water will get perfect Guppy water! If you absolutely must work in US gallons and ounces, you'll find my Brack Calc tool flips between both measuring systems as well as salinity and specific gravity. It's a free application and runs on Macs and Windows PCs. http://homepage.mac.com/nmonks/Programs/brackcalc.html Hope this helps, Neale.>

A few Kribensis questions 4/22/08 Good afternoon. My son's Kribs have become parents, and the fry have been swimming freely now for about a week. The parents and fry are in a well planted 14 gallon tank by themselves and the parents seem to be doing a great job herding them around and leading them to food (and not eating them). <Very good! Do check the pH though: if you have a pH above 7, you'll get mostly males; if the pH is below 7, mostly females. Tropical fish shops -- for obvious reasons -- only want equal numbers of males and females, so establish the pH and then decide whether raising the fry is worth it. Remember, surplus fry in the community tank will eventually get attacked by the parents as they prepare to breed again, and that's when things become chaotic (and bloody).> The stand on which the 14 gal aquarium is on is rather large, and he was recently given a 30 long (with lighting, filter, heater!) that he would like to eventually set there, but I was not sure what the reaction would be of the Krib parents if they partially drained their tank to move it with the Kribs in it to a smaller surface, or netted them all to a temporary container/tank then moved the tank and put them back if the fry might be endangered by the parents. <Parents will likely eat the eggs/fry, and then spawn a couple of weeks later.> If they do need to wait, what is the safest time/age of the fry to move the tank. The 30 might be their eventual home after it has been properly cycled in a month or two, which is also why they would like to be able to move it sooner than later to allow time for that. <You can't move parents and fry, and then expect the "bond" between them to be stable. Rather, you wait until one batch of fry is mature enough to rear yourself (which you could do right now, but is easier after 2-3 weeks) and then remove all the fry. Then move the parents, and let them start over.> Also, I have a tank with Kribs of my own and was wondering about salts. <Kribs do not need salt. What they ideally want is soft to moderately hard water at pH 7. Anything other than that is less than ideal, and causes problems with sex ratio in the brood.> I noticed that marine salt and cichlid salt has a lot of other trace minerals that a lot that plants actually like quite a bit compared to aquarium salt which is just sodium chloride, namely potassium, calcium and magnesium. <No relation here: the minerals in marine salt aren't the ones plants use. So one doesn't remove the need for another. The *elements* like potassium may be the same, but the minerals (*compounds*) are completely different. Similar to the fact we need oxygen to breathe, but can't "breathe" carbon dioxide, despite the fact that gas contains oxygen.> Are any of these salts safe using or beneficial in a community Krib tank (with barbs, glassfish) that also has an S.A.E. and Otos. <Glassfish are quite happy with salt, but none of your other fish want/tolerate salt.> If not, and hopefully not a dumb question, what are the non-salt tolerant fish non tolerant of specifically that are in these different types of salts? Sodium in any form? <It's complicated, and to do with pH, carbonate hardness, general hardness, and salinity -- all different ways of describing different aspects of the mineral composition of water. Every environment is different, and fish evolved to work in one set of conditions may not work in another. The best thing with community fish is to aim for soft to moderate hard, zero salinity, neutral pH water. Apart from livebearers, most community fish will be very happy with that. Cheers, Neale.>

Salt in FW tank 7/9/07 I just had a question about salt in freshwater aquariums. I was wondering if gouramis will do ok with salt in the aquarium. I'd like to keep my fish healthy with some FW salt. Thanks for all the help. <This is a simple one to answer. No. Do not add salt. The labyrinth fish group is a classic "primary freshwater fish" group, that is, one that has evolved in freshwater and has a low tolerance for salt. One a very few species naturally occur in brackish waters (the two I know of are Anabas testudineus and Osphronemus goramy). All the others require freshwater conditions, and mostly soft/acid conditions at that. Adding salt will be more or less stressful to the majority of gouramis. Now here's some more advice. There is no reason, none, to add salt as a matter of course to a freshwater aquarium. Tonic/aquarium salt doesn't raise the hardness or pH, so it doesn't help livebearers or African cichlids. Salt was used historically to compensate for poor water quality, because sodium chloride reduces the toxicity of nitrite and nitrate. But unless you have a really badly maintained aquarium, this shouldn't be an issue. Tonic salt is simply repackaged cooking salt sold at an inflated price to gullible and inexperienced aquarists. Even if you need salt to treat disease, as with Whitespot or fungus say, you could simply use non-iodised cooking salt for the same effect. And even then, you'd be using the salt as a short term treatment, not a permanent part of your maintenance routine. Unless you are keeping brackish or marine fishes, you shouldn't need to add salt to the tank, and in those situations you'd be using marine salt mix, not tonic salt. Cheers, Neale>

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