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FAQs on pH, Alkalinity, Acidity: Practical Science

Related Articles: pH, alkalinity, In praise of hard water; How hard, alkaline water can be a blessing in disguise by Neale Monks, Treating Tap Water, A practical approach to freshwater aquarium water chemistry by Neale Monks, The Soft Water Aquarium: Risks and Benefits by Neale Monks, Freshwater Maintenance, Treating Tap water for Aquarium Use

Related FAQs: pH, Alkalinity, Acidity 1, pH, Alkalinity, Acidity 2, pH, Alkalinity 3, pH, Alkalinity 4 & FAQs on: pH/Alkalinity Measure, pH/Alkalinity Adjustment, pH/Alkalinity Products, pH/Alkalinity Anomalies/Fixing, & Water Hardness, Freshwater Aquarium Water Quality, Treating Tap Water for Aquarium Use, Freshwater Algae Control, Algae Control, Foods, Feeding, Aquatic Nutrition, Disease

pH... measure is a "point", Alkalinity, a measure of downward resistance in pH, Acidity, a measure of upward resistance in pH.

Principally carbonates and bicarbonates serve ask alkalinity boosters.

Recommended Alkalinity: 10 to 12 dKH or 3.5 to 4.5 mEq/liter or 175 to 225 ppm...

I think you are missing a link. FW pH. Neat!     8/4/16
My name is Bob, I was browsing the links on your page (http://www.wetwebmedia.com/FWSubWebIndex/fwlinks.htm ) and I noticed that it
contains several useful resources.
I've been personally struggling with pH for quite a while and noticed that many websites contain a lot of incorrect and misleading information.
I decided to create a page to help other friends hobbyists that are dealing with the same problem and ended up with this: http://fishtankadvisor.com/natural-ph-control/.
<Very nice>
Have you seen it yet? It provides a lot of value to anyone seeking help with their tank. I think it could be an appropriate addition to your list
<I had not; and like the graphics; much of the info. presented. Might I proffer a suggestion? I'd change your word "titbits" to "tidbits">
Hope you're having a lovely day! Keep up the good work, and thank you for your page, I really enjoyed it.
<Thank you for your input and sharing. Cheers, Bob Fenner>
Bob Flickerton

pH, FW...   3/1/11
why is the pH of river water decreases after standing for 1 week
<Likely the loss (outgassing) of oxygen and taking up of ambient carbon dioxide... Aerate it and see. Bob Fenner> 

Abstract Questions from a Freshwater Aquarist   7/31/09
I just have a couple of questions that I couldn't seem to place under the same category (hence the name). Okay, my first question is can ph kill fish?
<Yes. Rapid changes alters blood pH, and this turn affects the ability of the blood to carry oxygen and carbon dioxide around the body. The wrong pH will severely stress, eventually kill, those fish adapted to particular pH levels. A Rift Valley cichlid for example will not do well at pH 6, and will become much more prone to opportunistic infections than otherwise.>
I recently bought 5 goldfish for my aquarium, I set the bags in the water for 15 minutes, then netted the fish and put them in my aquarium. Three hours later (literally) they all died. I checked my water chemistry soon
after, and the only offending thing I could see was a ph below the charts (anywhere from 5-5.4, judging by the color) Nitrate: 40 Nitrite: 0 Ammonia: 45-ish Hardness: Moderate Temperature: about 76 at time of death.
<Goldfish will tolerate pH values across a broad range, at least for a while, but they do best at basic pH levels between 7 and 8. If your pH really was as low as 5, then [a] biological filtration wouldn't be working,
and [b] that low pH could easily have shocked or killed the Goldfish outright.>
My second question: are store-bought fancy guppies of poor (I mean very poor) quality?
<Can be. Essentially the question is the same as this: which are hardier and more long lived, pedigree dogs or mongrels? The answer is of course mongrels, which, on average, consistently outlive their pedigree cousins.
Guppy breeders select in favour of certain traits, such as tails of a certain length, or particular patterns on the body. But they don't select in favour of hardiness or longevity By contrast, evolution selects in favour of "fitness", the ability to survive and breed. There's actually good experimental evidence that supports this. Fancy Guppies cannot be acclimated to living in seawater, whereas wild Guppies and "feeder" Guppies
both can. In other words, when breeders create Fancy Guppies, they seem to throw away some of the genes that made Guppies hardy in the first place. Now, there are differences in quality of Guppies just as there are differences in the quality of pedigree dogs. The Guppies you buy from a pet store were bred to a price, not a quality, and often fish farms use antibiotics to "support" their fish so that they can stock lots of them in breeding ponds without being too worried about healthcare. By contrast, breeders at fish clubs will be taking more care, selecting the best fish, and looking after each group of fish carefully, as a labour of love. None of this gets away from the fact that Fancy Strains are often very inbred, with father-daughter, mother-son crosses being very common, so even under the best of circumstances, Fancy Guppies are genetically "weak". But there is a difference between good quality fish and mass produced fish.>
I've heard that the guppy is supposed to be the easiest and most enjoyable fish in the hobby, and yet I've also had experience (and read on other sites) that suggests otherwise, mostly due to inbreeding and the breeders only selling low-quality fish to pet stores.
<Pretty much. Wild Guppies are astonishingly adaptable, and that's why they became popular in the first place. Fancy Guppies, like fancy varieties of most aquarium fish, are much less adaptable.>
My third question is if I breed natural (feeder) guppies with Fancy guppies, will (some of) the fry be fancy and hardy?
<No; they'll all be "feeder" Guppies, or at least, mongrel Guppies with a mish-mash of colours. To my eyes, such Guppies are lovely, resembling the wild-type fish, which are wonderfully variable. The old name for Guppies, Millionsfish, referred to the fact that there were so many of them, and every one was different.>
My last question is that I've heard (on this site and others) that Hornwort is an amazing and under-appreciated plant. That it eats up Nitrates and Ammonia, looks good, reduces water hardness, sucks up CO2, puts in O2, increases water ph, and is easy to keep. How many (if any) of those things are true?
<Like high-fibre breakfast cereals, while it certain does some good, it isn't a magic bullet that will cure all life's ills! Hornwort, or equivalent floating plants such as Floating/Indian Fern or Amazon Frogbit, are great additions to tanks with livebearers. Your Guppies will nibble at them directly, and also peck away at algae growing on the roots. Yes, they absorb some nitrate (and even ammonia) at a rate depending on light
intensity (i.e., growth rate) and yes, floating plants provide excellent hiding places for newborn fry. I strongly recommend them, but I would expect them to replace your standard protocols for water quality and water
chemistry management.>
I'm looking for a beneficial plant to re-place my withering ones (might help those plants if I turned off/down my air-stones), and then stumbled across the Hornwort.
<Hornwort does need strong lighting at tropical temperatures. It's less demanding in coldwater tanks and ponds. In tropical tanks, sometimes wastes away if the lighting is poor to moderate. Indian Fern and Amazon Frogbit are, in my experience, a bit more forgiving.>
Hope I wasn't any trouble!
<Cheers, Neale.>

Re: What's going on? FW quality  8/7/07 Hi Neale, <Hello Scott,> Thanks for the quick response, and sorry to bug you again, but... <It's fine...> I agree that the KH and GH is too low, but do not know how to raise them without adverse effects. Referring to the KH I use to use a phosphate buffer to control PH and it worked well but also caused hair algae, so I went to just baking soda, but if I add enough to raise the KH to the level you suggest then the PH raises to 8.0 and I prefer to keep soft/acid type fishes. (Discus on the way to go with the blue ram, Cory's and Pleco's. Silver dollars will go to the other tank.) Even the 7.2 is IMO too high and I would like to keep it lower at between 6.5-7.0. Any ideas there? <I personally always recommend against keeping fish in acidic water conditions unless you have to, e.g., for breeding purposes. There's no real advantage. Let's look at why. First of all, pH is a mirage. Fish don't "feel" pH. They only feel the total dissolved solids, since that's the only aspect that impacts their biology (specifically, osmoregulation). Adjusting pH up or down without first figuring out the correct General Hardness and Carbonate Hardness is like painting your motor car black and saying that turns it into a London taxi cab. So, forget about pH, and forget about buffers. Fish will adapt to a range of pH and hardness values, and silver dollars for example are fine in slightly alkaline, moderately hard water. The advantages to keeping them thus are two-fold. Firstly, water with appreciable levels of hardness (especially carbonate hardness) resist water chemistry changes. Secondly, the filter bacteria prefer alkaline/hard water conditions and hate soft/acid water conditions, so you get better water quality. Finally, all fish prosper best where the aquarist can do large, regular water changes. Most fish would sooner be kept at sub-optimal water chemistry values provided those values were constant (as they would be with regular water changes). Keeping fish are "optimal" values if soft and acidic won't help if the pH changes between each water change, as would happen if the water changes were small and the aquarist had provided no reliable buffering capacity to the aquarium.> The GH issue is that I use RO Right to reclaim the RO water and although the amount added does not give me a reasonable GH reading, it does give me a TDS reading of about 110ppm all by itself. <Any reason you don't mix RO water with plain tap water? I mix rainwater with tap water to get soft, slightly acidic water when required and it works perfectly. I use the ratio 25% tap water to 75% rainwater. You can use a Pearson Square to figure out the GH or KH of the water you produce by this method. Even a 50:50 mix should get something with moderate hardness and a neutral to slightly alkaline pH ideal for silver dollars, Corydoras, etc. The reason I say mix with tap water is its a cheap approach that combines the ease of large scale water changes with the buffering capacity present in many local tap water supplies. My tap water here has something like 20 degrees dH and a pH around 8.> I have heard that this is a good product, but I too would have expected its makeup to provide more calcium and magnesium or what ever the test kit tests for. Another possibility is that the test kit is faulty, but I have already tried 2 different test kits and have the same readings on each. <Probably is a good product, but fundamentally fiddling about with buffering solutions is hard work. Certainly, you should "practise" on disposable buckets of water to get the exact water chemistry you want before keeping any fish in it. I repeat, what matters with freshwater fish is *consistency* in the water chemistry, not what the actual values are. Within reason, fish will adapt to a spectrum of pH and hardness values.> As for the cloudiness I did try a water clarifier but that did not work. In fact it worsened the problem temporarily. <Odd. One thought might be a diatom bloom. This normally only happens in marine tanks, and the solution is a UV filter. I'd still tend to opt for breaking down the tank, cleaning, and returning the fish to the tank once cleaned. See if the problem happens again. I call this the nuclear option -- a bit like instead of faffing about with a computer trying to figure out the problem, you just erase the hard drive and put everything back. In the long run, a time saver.> I will have to try the vegetables, because the silver dollars hunt out the algae wafers even in total darkness. I know this because I have a night vision camera that I watched with after dropping a wafer into the tank in total darkness, and within 5 minutes or so the silver dollars will slowly zero in on the wafers by smell or what ever sense they have, and eat them. (can fish see infrared light? It sure made their eyes glow brightly). <No, fish can't see IR, though they don't need to. Their eyes are much more sensitive to visible light than ours, and some can also see UV to some degree. They also have a very good taste/smell sense plus the lateral line system for "touching" at a distance.> Hopefully they will not smell cucumber or if they do will not be interested in it. I have never fed them such so they may not recognize the smell as food and therefore leave it alone. <Worth a shot. You can't overdose vegetables because they contain so little protein. So sticking half a head of lettuce in a fish tank won't cause anything like the ammonia pollution of a one extra pinch of flake. I often leave big chunks of vegetables in my tanks for days at a time. The softer they become, the more the fish like them.> How do Pleco's get their protein? <From vegetables and algae. Because there's so little protein in 1 gramme of vegetable compared to 1 gramme of meat, Plecs need to forage more or less constantly, and will usually zoom right in on a meaty treat like a mussel given the chance. A few Plecs, notably the genus Panaque, can actually extract proteins from digesting wood something very few animals can do.> Thanks again, Scott <Good luck, Neale>

Water chemistry question  1/8/06 Dear WWM Crew: First, I would like to start off wishing everyone a very happy, healthy and prosperous New Year.  Thank you for your ceaseless and selfless dedication to making this site what it is.  You all have helped me once in the past and I hope you will help again.  My question involves water chemistry.  I have done quite a bit of reading, but I am still somewhat confused.  In testing our tap water, we found that it is a bit unfriendly for our fishy family members: ammonia 4-8 ppm, nitrite .5-1 ppm nitrate 20-40 ppm, <... these readings are dangerous for your domestic use...> TDS 220.  We were buying bottled water from the grocery store but that grew old fast because we have 4 freshwater tanks totaling 245g with a 5th tank (75g rainbowfish) in the works.  We took the plunge and bought an AquaFX Mako 5 stage RO/DI with chloramine buster attachment (by the way, it is a phenomenal filter, if somewhat expensive) which gives us wonderfully pure water.  I do understand about reconstituting the water.  I understand it is better to aerate the water for 24 hrs before buffering, and I do somewhat understand the relationships between pH, KH and GH. <Good> I have read here on WWM that a stable pH is more important than an 'ideal' pH <Yes> and I understand the reasoning behind it.  In my first attempt to make up water, my parameters are as follows, pH 7.6, 9 DKH and 23 DGH.  The pH pretty much matches the pH in the tanks now, with 2 of the community tanks at 7.6 and the other community tank and dwarf cichlid tank at 7.4.  I am using 1 teaspoon of baking soda, 1tablespoon of Epsom Salts and 1tablespoon of aquarium salt per 5 gallons. <Mmm, this is a bunch of Epsom, and possibly too much aquarium salt... I would dilute this by at least half> I will be taking another container and split this between the 2 before making more water to lower the KH and DH, but my question really is: can too much KH and GH be harmful to fish? <Depends on 1) the species, 2) what they've been raised in/exposed to, 3) what you want them to do, and 4) "other" factors... All have some range, tolerance to change...>   We don't keep Discus, but we do have some interesting fish including a black Ghost Knife and African Butterflies.  I know that some fish like a softer water to breed in, but we are not really interested in breeding fish at this time. Also, is it more important to pay attention to the alkalinity for keeping the pH stable, or treat the KH and GH equally? <More important to gauge, adjust alkalinity overall in most cases/settings... the calcium hardness is good to "judge" or keep at about half or so of general hardness...> Am I using too much aquarium salt to add back the trace elements? <Yes... I would use either a good general buffering product (made for aquarium use) or make one up here. Salts (combinations of metals and non-metals) have other properties... You don't want to "knock yourself out" trying to avoid salts altogether (they are present in all waters to a degree), but I would not purposely add much "back" to adjust your water>   To paraphrase Dr. McCoy: "Dammit Jim, I'm a computer technician not a water chemist!"  Thanks again for any clarity you can offer and keep up the awesome job. Thomas N. (Tom) Bilello <Understood... With the number of gallons total in your systems... I would rig up a system to "batch treat" your make-up water... engage a calcium carbonate addition as well as the/a bicarbonate (baking soda)... and likely leave this as it... Bob Fenner>

Alkalinity & pH 9/20/06 Hi! <<Hello, Angi. Tom>> When I measure my pH it is normal for my goldfish (7.5)...but when I test the Alkalinity it is low (40 - 80 ppm).   <<Okay.>> What should I use to raise the alkalinity and not raise the pH.  I have Buff-It-Up (which didn't do anything), Stable 7.5, and Alkalinity Buffer (I think by Sea* something).  This has me totally confused (I'm very new at this).  Oh, my water is hard from the tap.  If my pH is 7.5 which is alkaline why would my alkalinity reading be low?  I am sooooooooo confused!!!! <<Easy to become confused by all of this, Angi. Perhaps it would be beneficial to use the term "basic" rather than "alkaline" to alleviate confusion between the terms alkaline and alkalinity. (Works for me!) Okay, "alkalinity" is a measure of a sample's ability to resist changes in pH (downward) in the presence of an acid. By the very same token, "acidity" is a measure of a sample's ability to resist changes in pH (upward) in the presence of an alkali, or base. In simple terms, it's "buffering capacity". Where, on either side of "neutral", a sample tests on the pH scale, at a given time, has no bearing whatsoever on its "acidity" or "alkalinity". This is borne out by what you've discovered, i.e. your sample tested "basic" (alkaline) but its buffering capacity (alkalinity) is low. Frankly, this isn't a stable condition since naturally occurring carbon dioxide in the air mixes with water to form carbonic acid. Additionally, there are other organic acid "dynamics" that take place in our aquariums that compound the problem. What this means, to you and others in this situation, is that your pH levels are in a precarious position. (Just what you didn't want to hear, right?) Hence, you need to increase your alkalinity (buffering capacity) in order to resist a plummet from a slightly basic pH level (7.5) to an acidic one (>7.0). Here's where things get stinky, er, sticky. It simply ain't easy to increase alkalinity without raising the pH levels. Sodium bicarbonate (baking soda) provides excellent buffering capabilities due to the "bicarbonate" element but, if not added very, very judiciously, can drive your pH up dangerously. The products you mentioned above are, to greater or lesser degrees, of questionable efficacy. Honestly, I would look to small but frequent water changes rather than trying to chemically alter your water parameters. In the time that you'll spend playing around with various "buffers" and "stabilizers" as well as the requisite parameter tests to ensure that you haven't screwed up somewhere along the line, you could have, easily, performed a simple water change. In the long run, you might find yourself acclimating your Goldfish to pH levels outside of the "ideal" but, many credible sources suggest that you're better off keeping your fish at your tap water parameters than to "artificially" rearrange them.>> Thanks for you time. Angi <<Hope this helps somewhat, Angi. Best of luck. Tom>> Re: Alkalinity & pH 9/20/06 Thank you sooooo much Tom! <<Oh, stop. You'll make me blush.>> Frequent water changes is exactly what I'll do (I sort of enjoy it anyway).   One little question....when I'm doing like a 50% water change and gravel cleaning, would it be best to remove the fish to a bucket of the original aquarium water?   <<Angi, you don't really want to go with a 50% water change. That falls into the "massive" range. Keep it to about half of that and you'll be "golden".>> They are constantly sucking on my arms!! LOL!!! <<They like you, Angi! Nothing like some good fish kisses. :)>> I have 2 tanks (29 gal with 2 Oranda -- about 4" body size not counting fins)(40 gal with 2 moors and 2 Ryukins --- about 2" body size). I've decided to get rid of the gravel in both tanks.  It's a real pain trying to feed them because the only ones who see the food coming are the Ryukins.  The rest have to try to get what has fallen between the gravel (1/2" gravel)....so the gravel is outta of here! <<Oh, they'll scavenge, anyway. Won't be as much fun for them but, it'll be a whole lot easier on you!>> Take care and thanks soooooooooo much again!!! Angi <<You're most welcome, Angi. Tom>>

Re: lowering ph in planted tank   7/27/08 Neale, Well, I got a RO/DI unit (for a smoking good deal, so not sweating the cost, and have a use for the runoff H2O), the output of which is currently 0 TDS, 7.0 ph, and alkalinity is somewhere between 0-10 ppm. Just RO is about 16 TDS, alkalinity is same, ph is same. <All sounds promising.> My tap water is 420 TDS, 8.0+ ph (kit doesn't go above that), 130ppm alkalinity, and 210-220 calcium. <Standard issue "liquid rock"!> I mixed 50/50 tap and RO+DI, and I got 60-70ppm alkalinity, but the ph was still 8.0+ <It would be; acidity is created by the presence of acidic chemicals, not by reducing hardness. There's a complex thing behind pH involving the relative proportions of things that raise pH (alkaline chemicals, such as bicarbonate salts) and things that lower pH (acidic chemicals, typically organics such as tannins). What softening water does is reduce the abundance of the alkaline chemicals, so that smaller amounts of the acid chemicals will lower the pH.> I want to get roughly neutral ph with 70ppm alkalinity (to be safe...as you say 55ppm or so is a minimum target). <Sounds fine.> Seems like my main option here would be RO+DI and a neutral buffer to get my alkalinity up. Am I heading down the right track? <Yes, pretty much. I'd be using your 50/50 soft/hard water for starters, and to be absolutely honest not messing with pH just yet. I'd want to see how the background acidification of the tank affected pH between water changes (testing, say, ever 2-3 days). Once I was confident that pH was stable, I'd then look to using either carefully controlled amount of peat granulate in the filter to increase acidity or else using a pH 7 or pH 6.5 buffer salt as required. I like the Sera Peat Granulate; it's concentrated, so you can start off with tablespoon or three in a media bag, pop it into the canister filter, and then see what happens with pH across the next few days, checking pH daily. The water will turn brown of course, which may or may not be a good thing depending on your needs. Commercial pH buffers will "fix" the pH and keep water chemistry within a very safe range provided they are used correctly. They are more expensive than peat, but perhaps easier to use. But remember: pH itself doesn't matter much, pH stability does. If your aquarium is medium-hard to slightly soft in terms of hardness, it's already "optimal" in terms of fishkeeping. So medium-hard water at pH 7.5 would be fine for a wide variety of fish without any further fuss.> I am also trying to figure out how to mix some tap water in to get the calcium and some alkalinity help. Any suggestions on ratios? <Experiment, and see what you get. A 50/50 mix is ideal (as well as cheap to run in the long term) so I'd start there and monitor/adjust pH afterwards. Don't get dazzled by the idea there's some "optimal" pH because there isn't; instead understand the goal, creating water similar to the wild, by reducing carbonate hardness and adding organic acids such as tannins.> Thanks, as always, for the help. Paul <Hope this helps, Neale.>

pH in 29 gal FW Hello! First of all, I've really enjoyed your site. Very informative. <Ah, good> I have recently moved my 29 gal FW, and completely started over. I cleaned all the gravel and decor and the tank. I let the system sit for a week before adding fish. I have only added a barb and a diamond tetra and a Cory catfish. I am familiar with "new tank syndrome" and thought I knew what to expect. Even before I moved the tank, I was having problems with the pH going down. It was staying around 6.2 - 6.4 for the last 4 -6 months. <Sounds like your source water is lacking in sufficient alkalinity... you can easily add alkaline reserve... with simple baking soda, sodium bicarbonate, for instance> I have all plastic plants and rocks, a sunken ship and one ceramic (?) decoration. I have had this aquarium for over two years and have just started getting the pH drops within the last 6months. I thought that starting over might help but it has only been 3 weeks and the pH has dropped already from 7.2 - 7.4 (out of the tap, treated) to 6.2 - 6.4. Ammonia levels are normal. <Hopefully zero concentration of ammonia> The drop occurred after I put the fish in. It has been so long since I have had a "new" aquarium, I can't remember all. I knew to expect an increase in ammonia and nitrates, but don't remember pH going so low. Am especially concerned because it was happening before I moved the aquarium. I don't think it is our tap water because I have a 10 gal and a 5 gal that are doing just fine. <Mmm, they likely have some basic (as opposed to acidic or neutral) materials in them... like natural gravel, rock, other decor that is buffering the pH> I usually do approx. 10% water changes every 1 -2 weeks in all tanks, but have not started water changes in the 29 gal since moving it. (wanted to give the "good" bacteria chance to grow) <Yes, good idea> The fish do not seem to be stressed or unhappy, so I haven't done anything to change pH levels. I don't see much of the Cory, but then I never have. These fish are all over 1.5 years old. Should I just leave the pH alone and start with water changes? Should I go ahead and add more fish? <I would hold off on the new fish for a few more weeks... and consider either getting an alkalinity test kit (please read on the WWM site re the relationship between pH and alkalinity), or add about a tablespoon of baking soda (mixed in ahead of time in tank water) every day till you see your pH starting to be nudged upward to where you want it (about neutral, 7.0 or so). The baking soda is very safe added at this rate, and by keeping good records you can learn about how much you may want to add during your periodic water changes.> Thanks for your help Leigh Walker <You are welcome my friend. Bob Fenner>

Evaporation Chemistry Hello, A quick first question or two from a long time reader. <Welcome back> If water lost to evaporation is mostly pure water then why do I need to buffer the DI water I use to replace the lost water? Don't the buffers stay in the tank when water evaporates? <Mmm, they get "used up"... very basically (bad pun), the overall reactions in closed systems are reductive (as in Redox)... they tend toward making the water more acidic... in effect exhausting the alkaline reserve> Second, how do I determine how much buffer to put in the DI make up water? I'm using Seachem Marine Buffer per a recommendation in one of the FAQs. <Best way is to measure your water (new) and try adding your buffering product/s with testing... per your particular livestock, desires for GH, dKH...> Thanks for providing such a terrific service to all new folks. Regards, Jim C <Thank you for your participation. Bob Fenner>

pH change & Dead Guppies  3/16/04 I had an excruciatingly painful experience last night with my guppies!  I had put a bowl with the water from the aquarium itself inside this aquarium.  So it was the same water - I thought.  I put fish in it that were pesky or causing trouble to the community and so it was kind of like a "jail house" for bad fish.   <Hmmm, that's what breeder nets or quarantine tanks are for.> I had this bowl inside the aquarium for at least a week, maybe two, with a male platy who kept trying to "eat" my albino cat fish.  I was afraid he'd eat him alive eventually, so I put him in there.   <Kind of odd... My Cory catfish can hold up against dwarf puffer teeth.> Then there was a female guppy which had given birth to about 6-7 babies and was being hotly pursued by about 4 male guppies, so thinking she needed a rest, I put her in there.  I noticed that she had scoliosis, so wasn't expecting her to fully recover.   Then about two days later, I found her dead in the bowl.  I thought she'd died from the skeletal deformity she'd had, or something related to the stress from giving birth. <Probably tuberculosis, extremely contagious to humans-- http://reefkeeping.com/issues/2003-07/sp/feature/index.htm> The thing that got me yesterday was this:  I saw these 4 male guppies had begun to harass the other female guppy and were relentlessly chasing her, so I put all 4 of them inside the bowl to "do some time for bad behavior," and to give the female guppy a little rest.  Then, to my amazement, about an hour later, I was going to turn off the light to go to bed and I looked and saw that ALL 4 MALE GUPPIES WERE LYING DEAD IN THE BOTTOM OF THE BOWL!    I fished them out, and thought I noticed one's tail had disintegrated, but I'm not sure about that.  There others' were all intact, but they were all dead. I then checked the ph in the bowl and found the ph to be acidic, about 6.2 or so.  The water in the main aquarium was at about 7.0 or maybe 7.2.  So that's about 1.2 points difference!  I didn't think the water would be that variant since it was the original water from the aquarium, but I hadn't tested it since I put it in there about two weeks ago. <If there is no water flow getting into the bowl (like it would in a net breeder) then the ammonia & waste produces by your fish will build up in there, causing the pH to drop.  Your fish probably died from ammonia poisoning.> Meanwhile, the original platy is still alive inside the bowl with the acidic water and is showing no signs of stress.  Why, then did all 4 guppy males die within one hour or so after being put into the bowl???  The only possible explanation I can think of is that the ph change was too drastic for them!  Is that a possibility?  I thought they would be maybe stressed out by such a change, but not DEAD!!!  Please advise.  Is there some other possibility that I am not able to see?    <I'm afraid your platy is doomed in that bowl also.  Get a breeder net, or set up another tank for quarantine or to keep your more aggressive fish in.> Thank you very much for your thoughtful advise! <You're welcome & good luck.  ~PP> Leslie Wilson

pH in freshwater tank Hi, I had been using some cheap, not very accurate ph strips which told me that I had ph between 6 and 7.   Last night I received an order of supplies including some 5-in-1 test strips, called "scientifically and medicinally accurate" on the label. They place the ph of the tank (and our tap water) at closer to 8 or even a little higher.  Since the tapwater and the tank are the same ph I can only assume my tank has always been at that level.  As for the other readings, my water is listed as slightly over ideally alkaline (KH), between 180 and 300 ppm (but not as high as 300), between 150 and 300ppm total hardness or GH, 0ppm nitrite, and below 40 ppm nitrate. <<Hello. Perhaps you can take a sample of your tank water and tapwater to your LFS and have THEM test things for you, to see which tests the results compare to...for all you know, the old test strips may be the good ones. Impossible to tell unless you test these parameters with yet another brand of test kits. Two of them should match.>> The fish all seem perfectly happy in this environment and I don't want to really mess with it unless I am sure I am going to be able to make a permanent change.  I understand that slightly acidic water is generally better for freshwater tropical fish?   <<Which species? "Freshwater fish" like African cichlids need a pH of 8, while freshwater fish species like discus need a pH of 6.5. Yet both are members of the family Cichlidae. Same goes for all other species of fish, you need to research EACH species you want to keep, and try to choose species that have the same requirements, to keep together. Many fishkeepers have more than one tank, with more than one pH, keeping their various species happy. Also, remember to note the feeding requirements of the species that interest you...it can be difficult to feed slow-moving herbivores that are being kept with fast-moving omnivores... Also keep in mind that the pH of your tapwater can change seasonally, and will also change after being aerated overnight...your tapwater can go from 8.0 straight from the tap, to 7.6 after being stored in a Rubbermaid bin overnight...same water!>> I have currently harlequin and scissortail Rasboras, Cory and Otos, and am planning to get ghost catfish, cardinal and Rummynose tetras, and a Gourami or two over time (especially as I am able to get a good population of live plants going).   <<This sounds like a fine mix, most of these species will do well if you keep them in a pH from 6.5 to 7.5.>> Am I going to have to adjust the tank for these fish?  if so what do you guys recommend as a permanent, long term solution? Thanks, ~Anna <<If, indeed, you feel you need to lower your pH and soften the water for your fish, the easiest way is by using peat moss, sold at your LFS. But first double-check your pH with the LFS, like I said above. If the pH is still 8.0 from the tap, then store some overnight and test it again to see how far (or, IF) it drops. If you do these things and the tapwater still tests at 8.0, you can (as I mentioned earlier) store your extra water in a bin, run a powerhead in the bin to circulate the water, and keep peat moss in the powerhead media basket. It is quite easy to change your peat moss this way, and you will always have water change-water at the ready...the amount of peat moss you will need will depend on how far you want to drop the pH down. You may only need a small bit, you may need a lot. Depends on your source water. Test it and see. You may need to run a bit in your tanks filter, too, to keep the pH stable in the tank itself. Depends on your carbonate hardness. When it's time for maintenance, you then only need to siphon your gravel into a bucket, and hook a piece of Eheim hose onto your powerhead to refill the tank from your Rubbermaid bin. Piece 'o cake! :) One last thing...do you use an undergravel filter, and if so, how often to you clean it? You need to siphon your gravel (with or without an undergravel) quite regularly, since the detritus that builds up can lead to a low pH in the tank itself. All debris decomposes over time, and in the course of this becomes acidic, hence, a lower pH. Low pH problems in the tank water generally always means a good cleaning of the substrate is required. -Gwen>>

Low pH Levels Hello Crew <Randy> I have been reading your articles with interest in an attempt to understand why I cannot maintain a neutral pH in my fresh water aquarium. To be quite honest, there is so much information here I find it a little overwhelming, and also confusing. <Mmm, I frequently encourage folks to read the articles of a topic first... then the Related FAQs until they gain an understanding of facts, underlying principles... but it dawns on me that the accumulation, presentation of so much information, opinions may be disconcerting> I realize that this question must have come up dozens if not hundreds of times, but have found very few articles that match my problem. I have a 100 gallon freshwater setup that has been established for many years. I run an undergravel filter <Ahh, a source of enhanced reductive (acidic) activity...> with four powerheads, and a below the tank Eheim 2228. I do 50% water changes twice a month, with a gravel <A calcareous natural gravel I hope> cleaning, but find that the water in my aquarium is constantly too low in pH despite the fact that my tap water is very high in pH...off the scale in fact. <But of what alkalinity? That is, how much alkaline reserve? Water can be of nominally high pH, but not be well-buffered...> I use Seachem's neutral pH, but it seems to raise the pH for only a short while, usually only one or two days before it begins to rapidly drop off again. At one time I had some natural driftwood in the tank, but realized that this might be contributing to my problem, <Easily so> and eventually took it out. The tank is planted with artificial plants, and currently houses only Severums. I have six green and three gold, ranging in size from two to four inches. <How nice... and this species is tolerant, indeed appreciates soft, acidic water conditions> The fish seem to tolerate the low pH, but it seems obvious that they are not that happy. When the pH is closer to neutral, the fish are much more active. When the pH begins to drop, they tend to hide, and swim very little. <Yikes, good observations... most all life does not "like" sudden or drastic pH changes> It makes me nervous to be constantly adjusting the pH  artificially, and in addition, I can never seem to maintain a constant value, which can't be good for the inhabitants. It seems that most articles on your site deal with the opposite problem...people trying to lower their pH. I did read one article where you recommended the addition of some crushed coral to the gravel. <Yes, one approach... please see below> I understand that pH is related to many other things, and to be honest I find it all quite confusing. My question is...isn't there a good way to raise my pH and keep it up near neutral without having to constantly add conditioners and buffers to the water? <Yes, a few approaches> I would ask why my pH is always low, but I understand that there are many possible reasons, and would settle for finding a cure rather than understanding the mechanics involved. Any suggestions on how to raise my pH levels and keep them up without having to add lots of chemicals would be greatly appreciated. Randy <Your pH is low very likely simply due to a lack of bicarbonate, carbonate... content... If this were my system, I would develop a habit of using a designated bucket, plastic trash can... adding a teaspoon of simple Baking Soda (Sodium bicarbonate) per five gallons and letting it mix, heat it... for next time (I do weekly water changes on my cichlid tanks). Additionally, you might look into carbonaceous "natural" gravel, perhaps some stone/rock decor that will bolster your alkaline reserve, maybe add some "marble chips" to your canister filter... but not crushed coral to the tank. Do read about the concept of alkalinity, its relation to pH (one is a measure of "resistance" to change, the other a "point" on a scale...). You are close to a complete understanding here, and an operant solution to your vacillating pH trouble. Bob Fenner>

Re: Low pH Levels Hi Bob Thanks for the quick reply to my question. My tap water runs between 5-6 dKH, my aquarium water is near that, testing between 4-5 dKH. <Mmm, a  bit low... recommended that it be 10 to 12 dKH or 3.5 to 4.5 mEq/liter or 175 to 225 ppm...> I understand that gravel is a source for acidic activity, but I do clean it regularly with my water changes, <Mmm, the biological activity that results in acidification occurs whether the gravel is cleaned to a large degree> I use the Anaconda water siphon kit to accomplish this since I am dealing with rather large amounts of water. <Good idea> I have heard of aquariums with no substrate at all...do you recommend this in order to reduce the acidic activity? <Not in general... there are set-ups, reasons for some designs to do away with substrate/s, but the vast majority of aquarium systems are bettered by having them> As for the gravel currently in use, I have no idea as to its calcium content. As with all gravels I have seen at the local fish stores, it is merely labeled Mexican beach sand (gravel) or some other non descriptive label that doesn't give me a very good insight as to its actual chemical makeup. <Can be tested relatively easy... most simply with a bit of distilled or good RO water adding a bit of gravel, checking the resultant pH, alkalinity in a day or two.> This gravel is of varying sizes and colors and looks rather good in the aquarium, which was my primary reason for choosing it. If you can recommend a particular type/brand, or perhaps an online site that has a more complete description of its products, I would be sincerely thankful now that you have given me a clue as to what I should be shopping for. <At this point, I would add the more alkaline crushed material to your canister, add the baking soda to your change water... leave the gravel as is> As for the decor of the tank. I would love to add some rock(s) to the tank, not only for decor, but the fish also seem to appreciate having someplace to "hangout". <You are correct here> Would it be possible to give me some tips here on what kind/type of rock(s) I should consider adding. <Again, the simplest assay is mentioned above> Once again, it has been my experience that these things are displayed at the local fish store, but are seldom labeled as to their type...limestone, marble, or whatever. <You might even "collect your own", or check a local garden, rock and block supply outlet...> If you know of an online site where I could shop for these things, it would be most helpful to me. Locally there are only a couple of fish stores, and they are somewhat small with a limited selection of materials. <Dr.s Foster & Smith have about the best selection of aquarium supplies outright... seem to be fair priced, consumer-oriented> One other thing...I currently only clean my Eheim canister when the flow begins to bog down...maybe every eight weeks or so. Would it be helpful to clean it more often? <Mmm, yes... about once a month... a good idea to incorporate their Grob Flocken or such, or two "pads" that you can switch out just the outer, dirtier one, move the older into the "number one" position... to preserve nitrification> I read somewhere that flow should be your guide on this, but would be interested in your thoughts. <Better to not wait for diminished flow> I would like to thank you once again for your expert advise, and taking the time to share your knowledge with those of us with a somewhat...umm...lesser understanding. Randy <Glad to share, be of service. Bob Fenner>

Weird water chemistry Hi, <Hello there> A couple of weeks ago I wrote in about some persistent pH issues. I had been unable to keep my pH below 7.5 even with repeated treatments of acid buffer over several weeks. At the time I had thought the problem was due to alkalines in my gravel, which I had confirmed by testing a sample of gravel in a jar (with a second sample of plain old water as a control) and by testing the gravel with vinegar. <Good> Since then I have purchased a larger tank and am using a new substrate--Fluorobase (sp?). My water is pH 8.2 out of the tap, and the Fluorobase seems to have stabilized the pH at 6.6 ~without~ the need for RO or any acid buffer treatments! I've only had this tank running for a week now, but the Fluorobase really does seem like absolutely miraculous stuff for those of us with highly buffered tap water. <Likely has a good deal of laterite content> The transition from old tank (high pH) to new tank (low pH) revealed another factor in the pH change. I removed all the plants from the old tank to ensure there was no pH variation due to CO2. I also removed all of the gravel, which should have removed the alkaline source and allowed me to slowly bring down the pH until it matched the new tank-- or so I thought. What actually happened was that the pH ~kept rising again~. I'd add some water from the new tank, or a few drops of acid buffer, and I'd observe a small drop in pH as expected. But, when I'd test again an hour later, the pH would be exactly where it started! Ultimately I had to push the pH change much faster to overcome this effect. Fortunately everyone seems to have survived. <Dangerous... I recommend the use of an alkalinity test kit... treating new water OUTSIDE the system... like in a dedicated plastic can... ahead of use by a few days> I have since done some tests using the old tank, which is an Eclipse 3g. First, I thoroughly rinsed the tank. I removed the filter media but left the pump running. I filled it with dechlorinated tap water (pH 8.2) and added enough acid buffer to bring the pH down to 6.6. 12 hours later, the pH was up to 7.5. I added more acid to bring the pH to 6.6 again, and sure enough, 12 hours later, we're back at 7.5. Meanwhile, a control sample (water in a jug) remained at exactly 6.6 the whole time. <Okay> There is nothing in this tank besides tap water, dechlorinator, and acid buffer. So, it seems that the water circulation itself must be causing the pH to keep rising to 7.5! Speculations: (a) the acid buffer is evaporating, (b) the acid buffer is reacting with dissolved oxygen and losing its acid properties, or (c) oxygenation is affecting the pH through some other mechanism-- something else in the tap water. So, I shut off the filter, and 12 hours later the pH had dropped to about 7.0. This seems to definitively rule out (a), and point to (b) or (c) as the culprit.  <B likely> Has anyone ever heard of this phenomenon or care to hazard any guesses as to the chemistry of this? I am using Seachem Liquid Acid Buffer. All I know is that it is a non-phosphate buffer. Thanks, Dave <Oxygenation is driving the carbon dioxide from the water... it's leaving is allowing the pH to rise... again... you are almost "there" in understanding the relationship between pH, alkalinity/acidity and what you're doing... Read a bit more and you will know. http://www.wetwebmedia.com/FWSubWebIndex/fwph,alk.htm  Bob Fenner> 

Re: Weird water chemistry, take tres, David gets very close  Hi Bob, <Dave> Ok, so the "acid buffer" is reacting with bi/carbonates (KH) to produce carbonic acid plus insoluble carbonates, i.e. Ca(HCO3)2 --> H2CO3 + CO3= and then CO3= + ???. Carbonic acid then dissociates, H2CO3 --> CO2 + H2O. The CO2 is subsequently removed via circulation, allowing more H2CO3 to dissociate, so pH eventually rises again. <A good model, explanation> This would also be resulting in increased GH, and this is indeed what I observe: <Yes> Tap water: KH 60, GH 65, pH 8.2 Test tank w/ 2 doses of "acid buffer" w/ circulation: KH 25, GH 70, pH 7.5 But I also have: Display tank w/ Flora Base substrate: KH ~5, GH 80, pH 6.5 Seems like the Flora Base (I believe this contains volcanic ash) is doing a very good job (too good, really) in holding down pH, and it is eating up all my KH. I need to raise KH to minimize pH fluctuations, right? <Possibly... not be disingenuous, or overly-slippery here... it "depends" on a few other factors... For instance, will you have a "large" bioload of plants? These can/will aid you (and themselves) in ameliorating pH, KH and GH changes... types of foods added, amount of fish, invertebrate livestock will add their reductive influences (production of acidic wastes, carbon dioxide)... and regular maintenance... it may be that changing part of the water out on a... weekly basis? may be fine for keeping KH about right... Understand that the matter that makes up the KH is not necessarily irrevocably gone... but may be only weakly, temporarily bound up in your fancy substrate... this is what happens VERY often in "the real world"... with the hardness coming back into solution under certain conditions (particularly drops in pH)> So what is the best way to do this-- in a stable, consistent way?  I would like to achieve a pH of 6.8 with a decent amount of hardness-- this is a new tank w/only a couple of fish, so I haven't even begun to see any biological acids appear yet. Will adding crushed corals or seashells (in a bag in the filter) do the trick? Thanks,  Dave <I wish all aquarists had your good, inquisitive mind... The "best" way at this point is to proceed with actual stocking... and observe, test what actually ensues with the weeks going by... and then, if necessary, in addition to regular water changes, you might add calcium chloride to increase GH without elevating pH... Please see here re: http://www.thekrib.com/Plants/CO2/  Bob Fenner>

Re: Weird water chemistry Bob, <Dave> > [...] Seems like the Flora Base (I believe this contains volcanic ash) is doing a very good job (too good, really) in holding down pH, and it > is eating up all my KH.  I need to raise KH to minimize pH fluctuations, right?  > <Possibly... not be disingenuous, or overly-slippery here... it "depends" on a few other factors [...] Understand that the matter that makes up the KH is not  necessarily irrevocably gone... but may be only weakly, temporarily bound up in  your fancy substrate... this is what happens VERY often in "the real world"...  with the hardness coming back into solution under certain conditions > (particularly drops in pH)> Hm.  Now that raises the concept of "buffering" to a higher, hence juicier, order of complexity.  However, I talked to a tech at the company that distributes the stuff, and he assures me that the KH is indeed gone, not bound.  A little experimentation is in order here... <<Could be and sounds like it>> > So what is the best way to [raise KH]-- in a stable, consistent way? [...]  > <[...] you might add calcium chloride to increase GH without elevating pH [...]> I do want to add KH, and raise pH, so that I can begin injecting CO2.  But, since my fancy substrate vaporizes KH, I need a way to do this slowly and constantly, as opposed to adding pinches of baking soda or CaCl or what not. <<These are the safest methods...>> I recall reading somewhere that CaCO3 and MgCO3 are more soluble in acid water (i.e. something like CaCO3 + H3O+ => Ca++ + HCO3- + H2O) <<Calcium more so than Magnesium carbonate...>> so wouldn't adding a small amount of limestone to the tank/filter therefore not only raise the KH and pH (which is desirable here) but also to buffer the system against drops in pH?   <<Yes...>> My continued thanks for your guidance... -Dave <Do experiment here... there are a few "formats" of calcium carbonate... limestone, marble, aragonite... powdered, aggregate... Bob Fenner>

Re: Weird water chemistry Any recommendations as to which CaCO3 supply would be best given my environment (ready solubility in mildly acidic environment, small tank, heavily planted, desiring enough buffering to permit CO2 injection)-- viz. limestone, marble, aragonite?  Crushed coral? <Yes... I would use a Dacron bag to hold a given (weigh it) mass of Aragonitic sand of a given grade (3-4mm or greater diameter) and place this in your water flow path. Not too soluble (low enough Ksp, http://www.google.com/search?sourceid=navclient&ie=UTF-8&rls=GGLD,GGLD:2004-27,GGLD:en&q=solubility+product+constant ) Bob Fenner>

Re: Weird water chemistry Thanks! <Welcome... I look forward to our further chatting... there IS a great deal that could/can be discussed re petfishing and chemistry... but not much that REALLY is of practical consideration... relative to all the other fields the hobby entails! Bob Fenner>

Re: Weird water chemistry Same here, Bob.  I am a tinkerer at heart, project manager by trade... have yet to see a better example of a "dependency-driven resource management system" than an aquarium.   <Ha!> I must admit that I do take perverse pleasure in contemplating the complexities of water chemistry (pain/pleasure being another complex buffered system) but your point is well taken. <Ah, good> So, on another topic-- livestock selection for a specific niche.  I have a 12g cubical tank, more-or-less Dutch-style, back 1/3 forested up to the top of the water column, medium-height plants front-left and (hopefully) a Glossostigma bed front-right.  Population is currently 1 Betta, who lurks around the bottom when he's not coming up for air or gearing up for an attempted leap into the sump, and a small school of H. Rasboras who more or less stick to the large front-right open area, plenty of room for their shenanigans there.  I may also need a SAE or flag for algae control, though I've been warned about flag/Betta combo. <Can become irksome "riders"...> I am looking for a species that will prefer the mid/upper planted areas, ideally small (<1") schooling fish (I think I can support 4-5 more if they are really tiny).  I am not fond of tetras in general.  Do you have any suggestions? <Some of the smaller Danios, livebearers like Endler's, Hatchetfishes if you have a cover (your allusion to the Betta leaping out), even other labyrinth fishes like the smaller gouramis of the genera Colisa and Trichogaster come to mind. Bob Fenner>

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