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FAQs on Tap/Source Water Use for Aquariums

Related Articles: Treating Tap water for Aquarium Use, Water Purification Using Reverse OsmosispH, alkalinity, acidity, Freshwater Aquarium Water Quality, Freshwater Maintenance

Related FAQs: Freshwater Aquarium Water Quality, pH, Alkalinity, Acidity, Freshwater Algae Control, Algae Control, Foods, Feeding, Aquatic Nutrition, Disease

Starting with "clean" water is often the best approach... then adding materials to make what you want. An oddball for sure. A Polynemus/Bobo species in a bare-bottom system.

pH spike in freshwater tank on well water     12/25/14
Merry Christmas! I have a 400 gal. holding tank (catfish, tilapia eventually) that I've just constructed with inert materials (fiberglass, pvc, polyethylene) and have dechlorinated my supply water (from a MUD well) through carbon before entering tank. MUD says they do not use chloramine or buffers, but we have a chloramine removal tower anyway. Supply water enters tank at pH of 7.7 and rises to 8.8 in 10-12 hours of circulation/aeration.
There are no animals in the system yet. Samples from nearby tap act the same with aeration. Hardness around 75, alkalinity around 300, TDS around 400, and pH has been tested via strips, colorimetry, and pH meter. Water is from a well located in far SE Texas and sodium approaches 400 mg/l as listed in their annual water quality report. Buffers such as API Proper 7.0
have a short-term effect (1 hour), and muriatic acid 3-4 hours, but the pH always spikes back up. System runs normally at 60 gpm, but this occurs at slower flow/aeration rates as well. Any ideas as to what may cause this?
Thank You!
<Dissolved CO2 is the commonest cause for these rapid pH rises. Under pressure and/or at low temperatures the water holds more CO2, but once drawn from the tap, the water pressure drops and the temperature rises, causing CO2 to be released. Without the dissolved CO2 (which produces carbonic acid) there is less acidity to neutralise the alkalinity in the
water, so the pH rises. This is very similar to the daily pH changes by day and night seen in ponds, where photosynthesis (which uses up CO2) causes pH rises and when photosynthesis stops (allowing dissolved CO2 to accumulate) the pH goes down. There's no fix as such, but you can draw the water, let it sit/aerate for a time, and then use it after the pH has stabilised.
Alternatively, if you make just small water changes (say, 10-15% at a time) then the bulk of the water in the aquarium will minimise the impact of the relatively acidic (lower pH) water added straight from the tap. Most fishes can handle minor pH changes quite well provided ambient hardness and alkalinity are relatively stable (obviously, Goldfish and Koi have to
tolerate this in ponds, as do most fish in densely planted shallow water habitats). Merry Christmas to you too, Neale.>
Re: pH spike in freshwater tank on well water

Quite impressive response time, especially on a holiday! Thanks!
<Most welcome. Neale.> 

Ionized Water -- 08/06/09
Please tell me if Ionized water from an Ionizing filter can be used for fresh water fish?
<What, pray tell, is ionised water? Any water with dissolved minerals will contain ions. Hard water fish will want a particular selection of ions (calcium, potassium, carbonate, bicarbonate, and sulphate, in particular).
Soft water fish rather less, but still sufficient to maintain a stable pH and provide an adequate substrate for various biological reactions.>
The pH us between 7 and 8. and it has an ORP of -250 mv
<Water with a pH between 7 and 8 is ideal for a variety of community fish.
However, this is ONLY the case if the general hardness and carbonate hardness are within normal ranges as well. It ALSO assumes that other, potentially toxic, chemicals such as ammonia and copper are removed. Water that has been treated in such a way to make it taste better (or at least different) might be good (or at least harmless) to humans, but not necessarily idea for fish to live in. Frankly, most people will do better keeping their fish in plain vanilla, unsoftened tap water. Tap water is typically very safe, once you remove the chlorine and chloramine, and relatively high levels of carbonate hardness make it resistant to the
background acidification natural to all aquaria.>
Thank you, George
<Don't put anything into an aquarium that isn't expressly sold as "for use in aquaria". If the product doesn't come with this recommendation, then don't use it. Simple as that. Cheers, Neale.>

Re: Ionized Water (RMF, comments on anti-oxidants in water and millivolts measurements, please) 8/11/2009
Hello Neale
Your reply was very helpful as keeping fish is completely new to us and although we have learnt a lot from your website, the info you gave was specifically helpful.
<Glad to help.>
Is it possible to take the question a little further you directly or do I have to address further inquiry to the general website. The particular water ionizer I have has a charcoal filter which takes out chlorine,
phosphates and lead, and leaves in the Potassium, magnesium, calcium and sodium. The pH is controllable to get anywhere from 7 to 9.
<In theory, it sounds fine. But without actual numbers in terms of mg/l calcium carbonate (or degrees KH) and mg/l calcium oxide (or degrees dH) it's difficult to be categorical about this.>
Finally the water is anti-oxidant meaning it comes out of the machine as a hydroxyl ion with a negative charge of -350mv when measured with an ORP meter.
<No idea whether being "anti oxidant" is of use for fish. I'm going to ask Bob for a second opinion here, since RedOx values are more studied on the marine side of things than the freshwater.>
<<Is Oxidation-Reduction Potential... a measure of the capacity of a solution to undergo loss-gain of electron physical (more than chemical) reaction series... Please see here: http://wetwebmedia.com/SystemPIX/RedOx/RedoxPPTpres1.htm
and the linked files above. A useful "window" into water quality for marine systems particularly... not so much for freshwater. The measure presented (though in positive, not really negative charge) is fine for use here. RMF>>
Can my daughter use this water to fill or top up her fish bowl. The first goldfish we bought her died even though she was using bottled water which she was told was reverse osmosis water.
<RO water will kill fish. Let's be crystal clear about this: fish cannot live in distilled water, deionised water, or pure rainwater. While these are used in aquaria, they are ALWAYS mixed with tap water to raise the pH, hardness, and carbonate hardness. My fish typically enjoy 50/50 tap water and rainwater. Goldfish prefer hard, alkaline water, the equivalent of water that's percolated up through a chalk aquifer. A pH of 7.5 to 8, a hardness above 10 degrees dH, and a carbonate hardness of 5+ degrees KH suits them well. If you have hard tap water (i.e., things like kettles "fur" up easily) then you have perfect water for Goldfish. What Goldfish don't like is soft water, and RO water would be lethal.>
We would like to learn more before we buy another gold fish.
<Much to learn, I fear. The use of the killer phrase "top up her fish bowl" suggests a bunch of things. Firstly, you were using a bowl. Don't. Just don't. Secondly, you didn't have a filter. You need one. Finally, you were topping up the water rather than changing it. For Goldfish, a 20-30% water change every week is a good idea. Other than adding dechlorinator, hard tap water is ideal just as it is! So, instead of worrying about expensive anti-oxidising whatever water, concentrate on the basics: a 30 gallon tank, a filter rated at 6 times the volume of the tank in turnover per hour, lots of fresh green foods, and regular water changes. That's all there is to keeping Goldfish. See here:
Most everyone who has problems with Goldfish does so because they ignore the basics, willfully or otherwise.>
Hoping to hear from you.
<Always glad to write back.>
<Cheers, Neale.>

Water?   4/10/09
I have been searching and reading and really trying to wrap my head around water chemistry and what is going on in my tank.
<By default, leave your water chemistry as it is out of the tap, while ensuring you don't do something silly like use untreated tap water or water from a domestic water softener.>
I have 25 gallon with 2 honey Gourami, 3 Guppies, and 3 Swordtails now.
<Not really a compatible selection of fish; Guppies and Swordtails need hard, alkaline water, and in the case of Swordtails, not too warm. So pH 7.5, 10+ degrees dH, at 24 degrees C would work fine for them both. As for Honey Gouramis, these are Asian stream dwelling fish that need warm, soft, acidic water. So for them to last any length of time you're looking for 5-10 degrees dH, pH 6.5-7.5, 26 degrees C. As you can see, there's not much overlap between these three species, so if you get conditions right for one fish, another will be under improper conditions, and therefore likely to get sick.>
I had 6 Guppies but 3 have since died as well as both my frogs and I think it has something to do with my alkalinity and my PH. I bought a package of a different kind of test strips because they were on sale ( my first mistake) and it was very vague on the readings and hard to get exact readings.
<Frankly, test strips are fine for ball park values, even if they're not especially accurate. All you really need to know is whether your water is hard or soft, has high carbonate hardness (alkalinity) or not, and whether
the pH is above or below 7.>
I thought I'd tough it out till I finished them and do my regular routine (second mistake). My nitrates, nitrites and ammonia are fine however since going back to my normal test strips have discovered my PH has gone from 7.2 to 6.8 and my alkalinity from 120 to zero.
<Why is the alkalinity so low? This is extremely dangerous, and likely why the pH is dropping. Are you using tap water or water from a domestic water softener.>
Should I leave it as is or should i do something like baking soda to raise my alkalinity?
<If your water really is this soft out of the tap, then yes, you should be raising the carbonate hardness somewhat, to around 5 degrees KH. I'd recommend using small portions of home-made or store-bought Malawi (Cichlid) salt mix, starting at about 1/4th to 1/3rd the recommended dose for usage in Malawi and Tanganyikan cichlid tanks. The recipe for making your own is on WWM if you want to save money; it's cheap and easy.>
I know it will probably increase my PH but can I do it in a way it will be real slow as to fix the alkalinity and not kill any more fish?
<Fish don't "feel" pH; but they do get harmed by pH changes.>
Thank you for your help,
<Hope this helps, Neale.>

Re: Water? 4/10/09
Thank you so very much for your information. I'm on a well system, could this be the cause of my soft water?
<Every well is different! Usually wells are sunk into limestone or chalk, where the aquifers tend to be, so the usual thing is for well water to be somewhat to very hard. Use a test kit (test for carbonate hardness,
ideally) and find out what your tap water is like. Remember, don't use water from a domestic water softener, if one is installed; if one of these is installed, the drinking water tap in the kitchen usually bypasses it.>
I will definitely try your recipe and hope it all goes well. I lost another guppy this morning :(
<Oh dear. Do review water chemistry, and it's importance to successful fishkeeping. Once you know the hardness and pH of your tap water, it is ALWAYS best to choose fish that prefer such conditions.
Cheers, Neale.>

Re: Water? 4/10/09
Sorry to bother you again but I was wondering if my water conditioner may be causing the issue?
<Shouldn't do.>
I tested my water straight from tap and it showed PH 6.8 and KH 100 with GH at soft.
<OK. This is going to be good water for soft water fish such as tetras and Corydoras, but bad for livebearers (guppies and the like).>
I added a little of my water conditioner (stress coat+ from API)
<An excellent product.>
and tested again it showed PH 6.8, KH 100, but my GH when down to very soft.
<More likely to be variation in your test kit. Wouldn't worry unduly.>
Is there a better conditioner to use and would you still recommend the salt recipe if I change conditioners?
<Would recommend you accept the water for what it is, keep soft water fish that don't need hardness, under stock the tank, and do regular (25% weekly) water changes to offset background acidification. This would be the "easy" approach, anyway. If you wanted to keep hard water fish (such as livebearers) then yes, you would need to raise the carbonate hardness through the use of Malawi salt mix or similar. Do remember "tonic salt" and "aquarium salt" aren't what you need here! Often people make this mistake;
it isn't salinity you're raising, but hardness, specifically carbonate hardness, because that's the thing that raises and steadies pH at the desired 7.5-8 level things like Guppies prefer. Cheers, Neale.>

Water Conditioner Question  9/10/08
Dear WWM Crew,
I have a question regarding water conditioners. For years I have been pretreating my tap water with a water conditioner that eliminates chlorine, chloramines and ammonia. I read that I do not have to necessarily treat my tap water with any water conditioners?
<Incorrect. While chlorine will diffuse out of water over time, chloramine is much more stable, and in the process of decay leaves behind ammonia. Ammonia does not diffuse out of the water. Likewise copper and heavy metals from the plumbing system will be left in the water. In short, if the water contains chloramine or copper, you MUST use a water conditioner.>
I can just add my tap water to an empty water bottle and age it for approximately one week and all the chlorines, chloramines and ammonia should escape.
<No. Only chlorine leaves by itself if the water is aerated for a day, or left sitting for a week. Everything else in the water stays put.>
I know a few people who have freshwater aquariums that do not pretreat their tap water with any water conditioners; they just age their tap water for approximately one week and their fish are doing just fine.
<Just because you play a round of Russian Roulette and survive doesn't mean the game is safe. The problem with this type of anecdote is you have no idea what fish they're keeping (some species are more tolerant of pollution than others) and how long those fish are living for.>
Is this true; have I been wasting my money for years?
<Dechlorinator costs very little. I buy the pond-size bottles for around £10 and that lasts me a year. Of all the things you can do to keep your fish, this is one of the best and least expensive.>
Please give advice. Thanks Jean
<Cheers, Neale.>

Re: Betta... conditioner dosage   5/30/08 Hello, just an update from before. <... John, w/o the prev. corr. I/we have no idea what you're referring to... there are a couple of dozen of "us" here> I got Prime by SeaChem water conditioner and Maracyn. I also have a 10 gal tank. Right now the Betta is in a hospital tank with the Maracyn. I had a question can I dilute the water conditioner by putting a 1ml dose in 100mil's of water then only using 50mil's of water meaning it would be at half strength or this doesn't work with water conditioners. <Does not... they're formulated/concentrated to treat a given "amount" of sanitizer... in some municipalities, times, the "limit" of their capacity at the stock dosage> Also I don't seem to see it anywhere, how would I put him in the 10 gal tank without stressing him out to much. I pictured 10 gal's would be bigger then this. Thanks again for the previous help. J. M. <Not following you here... a ten gallon should be more than enough room... given it is heated and filtered, for a single Betta. Bob Fenner>

Blackwater extract use with a Betta, Tank    3/29/06 Hello to all you good folks! After reading your forum for quite some time I have learned to ask a question before I attempt anything new with my small tank. I was wondering about Blackwater extract and whether it would be suitable for a bachelor Crowntail Betta in a Hex 5 filtered and heated tank. Water parameters are ammonia 0, nitrite 0, nitrate a trace to 5, moderate hardness and alkalinity, pH 7.6, temperature a constant 78 degrees. This is the first week of a 20% weekly water change from tap water (conditioned with Aqua Plus) to bottled accomplished by mixing 25% new to 75 % old, followed by a 50/50%, 75/25% and finally a 100 % switchover. My tap has become suspect after much sewer system upgrading by the town. So if Blackwater extract would be beneficial for my guy how would I incorporate it into my water changes? <Can be added directly to the water in the tank, or to the new water to be used during water changes> Would I mix it with my new hybrid gallon of water and test for pH and hardness? What would be acceptable parameters for any sort of change in these two entities? <Likely no need to test. Won't affect that much> Any help would be greatly appreciated. Oh, by the way, I have never been steered wrong by any crew member and that "gentleman" should be reminded of that by any and all the people you have aided throughout the years!! Thank you very much. Sue :) <Thank you. Bob Fenner> R/O Water For FW  - 03/12/2006 You folks have been so great with my saltwater questions, now I will try my luck with freshwater.  I have a 55 gal with just a few angel fish and a couple danios.  I am hoping to keep some Cory cats, but my tap water quality isn't that great.  I have invested in RO/DI system and think I finally have it figured out for my saltwater.  What do I need to do with it for freshwater to keep angels and Corys?  I will probably be using a 5 gal bucket to store the change water in.  Besides aerating it, what should I do as far as ph and buffers for freshwater? < Depending on how hard your tap water is, I would recommend a mixture of 50% tap with 50% R/O. Based on your fishes reaction you could increase the R/O portion to 80%. I would not go 100% R/O unless you added a good buffer.-Chuck> Thanks, Donna

Re: Softening Hard Water  - 03/12/2006 My TDS meter says 138ppm.  I am not sure how "hard" that is, but I do know that it has a lot of phosphate which most likely is the reason for the algae. < A TDS meter reading of 138 would mean that you water is moderately hard. Soft water would be under 75 ppm. So a 50% mixture of R/O with no ppm and you tap water would give you a TDS of 69 ppm. Start there and see how you fish react to it. I bet they like it.>   What would I use to buffer 100% RO/DI with and what would the procedure be for it?  Would I buffer my 5 gal container of aerated RO/DI water or buffer the tank when I put the aerated RO/DI water in? < I never make any water chemistry changes in the aquarium. Pour a 5 gallon bucket full of tap water. Check the pH and TDS. Measure it again in 24 hours. Any dissolved CO2 gas should have off gassed  by then and you will get a real pH reading. Pour half of it out and fill it up the rest of the way with your R/O water. Let it sit for 24 hours and check it again. If your water is under 75 ppm it is soft and start to use this bucket of soft water to start doing your water changes. After a few water changes your aquarium water will become softer over time. If you wanted to use R/O straight then you need to add some chemicals back into the water.  Kent marine makes one called R/O Right.> I would think that using the RO/DI water would be done in many small water changes to acclimate the fish? < Gradual is the way to go.-Chuck> Thanks for the quick reply, Donna Hornwort as a Water Softener? Hello WWM Crew, An uncharacteristically brief questions from me, this time. I have read in a few places that hornwort will soften water. Is this true? If so, should I remove it from my cichlid tanks? Thanks, Ben < This is really an amazing plant that doesn't get enough credit. I saw hornwort all over the bays and inlets in Zambia while diving in Lake Tanganyika a few years ago. It looked like little wire brushes. When I returned I read up on this plant and found out that it actually gets its carbon dioxide from breaking down the bicarbonate in the water. Pretty amazing. During the process CO2 is removed and you get a calcium carbonate that actually increases the pH. Since coming back I have added hornwort to all my African tanks because they can handle the hard water and do a great job absorbing nitrates from the water.-Chuck> How to use GH+ Botanica product? I am not sure how to use the GH+ Botanica product to raise only General hardness. I have a tank of 28 gal, with two goldfishes in it. The GH of my tank is 5 German degrees. For how many more degrees should I raise it? <Another five or so> In the instructions says that a capful (5ml) will raise 5 gal of tap water of two GH degrees. My second question is: Can I pour it directly in the tank for 28 gal or should I do it slowly, like adding one capful each day for five days so that the whole gallonage gets conditioned?  <Better to do this slowly... and going forward, to pre-treat new water before using it> Thank you very much, I appreciate your help <You're welcome. Bob Fenner> 

Confused about GH advice from Marina >Thanks Marina for your help, but I did find confusing your advice about not messing with General hardness. It was advised from Bob Fenner to raise my GH of 6 dGH which will bring it to a total of 10 dGH. >>If we're talking about goldfish (actually, just about ANY captive-bred tropical fish) here, I would not mess about with it. Goldfish are incredibly flexible when it comes to particular water parameters, they can take very soft water with a relatively low pH, all the way to parameters necessary to successfully keep Lake Victorian African cichlids. If your water is well-buffered it will likely bounce back and forth (the carbonate hardness, or alkalinity), which is far more stressful in my opinion than letting it be and allowing the fishes to acclimate. Trouble can be even further exacerbated if the pH is also affected by changing the hardness, and that WILL kill your fish. >But now you are telling me to not mess with these parameters. What should I do now? Please help me clarify this issue. Thanks again Marina. Marcellino >>Ok, let's try it this way - if you didn't test for hardness at all, could your few problems be solved and/or answered any other way? Yes. Can they be attributed to anything else? Yes. You have a brand new setup, which, due to being over-cleaned a bit, will continue to have some unstable parameters. Those most important in this case are those which indicate the establishment and culturing of nitrifying bacteria, which are the consumers (oxidizers) of ammonia and nitrite. The end result of these efforts, and the only reading you should get any positive result for, is nitrate. None of this is affected by hardness to any degree we need to worry about (especially with regard to goldies). If you'd like a more succinct, clearer explanation of GH, KH, and how they affect water parameters, try the following: http://www.algone.com/water_parameters.htm  http://www.aquariumpharm.com/articles/gh-kh.asp  I do hope this is more helpful, and I will remind again to not mess about with the tank so much. Marina

New to the hobby and all its water quality issues, arcane terminology! Bob,               I am new to this whole fish stuff.  My fiancĂ©© convinced me to do it and it's not going so well.  I have a 30 gallon tank with a heater and a penguin 170.  Currently there is 3 Plecos and 4 Dempseys and 3 convicts in the tank. < Your Jack Dempsey's get up to 8 inches long and will eventually get too big for your tank.>    I am having some real ammonia problems lately, and after contacting my LFS I have done everything they told me to do. Frequent water changes.  And use ammo lock.  But I hesitate to do that; I gave it a try anyways.  Now for some reason my ammonia has spiked beyond even 8.0ppm (I know its higher but my testing kit only goes to 8.0) Anyways the nitrate is going up as well but the ammonia has not changed a single bit.   I do not know exactly what is going on. < Here is what is going on and how to solve it. First check the ammonia of your tap water. Many water systems now use chloramines instead of just chlorine. Chloramines are a combination of Chlorine and ammonia! Check your tap water with your ammonia test kit. Not all water conditioners get rid of chloramine and this is what you could be reading on your test kit. Use Amquel from Kordon or a new product called Ultimate. Both will tie up the ammonia. Usually what happens in a new tank is the fish excrete waste and any left over food is broken down into ammonia, especially in an aquarium in which the pH is greater than 7.0. In an established tank the ammonia is broken down into nitrite. This is less toxic than the ammonia but is still not good. This may take a couple of weeks. Eventually the nitrites are once again broken down into nitrates. These are not good either but they are the least toxic of the three. Nitrate levels should be kept no higher than 25 ppm, but some fish can take them as high as 50 ppm. Make sure you are not overfeeding and make sure you clean the filter often. The excess food may be accumulating in the filter and adding to the problem. You need to get the waste out of the system on not just let stay in the filter.> After calling the same LFS they told me to do a huge water change.  90%, which I did very carefully as to not harm the fish.  I ran the test again and my ammonia is still sitting at 4.0ppm.  And all I left was 1 ½ inches of water. < Fill up the tank and keep the system running. You may have too many fish to get things started. The good news is your fish are fairly tough. Fill up the tank, feed once a day with only enough food that you fish will have it all consumed in a couple of minutes. Get a 5 gallon plastic bucket and check the water for chloramines and treat according to the directions on the bottle. Check again and make sure it works. You may still have the ammonia in the water but it may be ties up by the chemicals and reading on your test kit. The water should be clear and have no odor. Ammonia makes the water very cloudy. If the water is clear and the fish are doing fine then I would not worry too much about the test kit results.-Chuck>  I do not know what is going on any insights as to help with this?   I am attaching some data below for you're review as well.  

Kordon's Amquel Plus? Hi to all at WWM: <Hi! Ananda here tonight....> I was wondering if any of the crew had used this product? <Judging by the fact that the response got delayed a bit, and I just saw your email today, I'm guessing not...sorry about the delay.> I was previously using the regular Amquel to treat my make up water for each water change. <Okay> Two weeks ago I decided to try the Amquel Plus instead. I have a what I think a heavily stocked 110gal FO tank. I perform 6 gal water changes twice a week and test the water regularly and I seem to maintain a nitrate reading of approx 25ppm. <Hmmm. Time to increase your filtration capacity, amount of water changes, or both if you are concerned about this nitrate reading. Have you considered live rock?> However, one day after using the Amquel Plus the nitrate was zero. During the last two weeks I tested my water and the nitrate increased to about 20ppm. I used the product yesterday and now this morning the nitrate was zero again. I am a little concerned about now effective this product is, maybe too good to be true? I am not sure how this product works and is there a problem with such fluctuating nitrate readings. <Well, I'd prefer there to be a generally lower level of nitrates...but the reason for doing water changes is to keep the nitrates down. I suspect many tanks go through nitrate fluctuations like this. That said, I did a little research on "Amquel+", as the product literature calls it. The short story is, Kordon is not releasing any info about what's in the product, because they've got patents pending on the stuff. For how it works, they're referring to how Amquel works as an similar product. For the long story, check out their web pages: http://www.novalek.com/kpd79.htm for Amquel+, and http://www.novalek.com/kpd51.htm for original Amquel.> I appreciate your thoughts on this one. Thanks, Gene <Read their literature, find out what others think about it, then make your own decision... a good general plan of attack for most products. --Ananda>

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