How can I lower the KH of my tap water?

Discussion in 'Aquarium Water' started by danhammond, Apr 12, 2012.

  1. danhammondNew MemberMember

    I have done a lot of research on this and I find a lot of advice that simply does not work for me.
    So I am very confused what is causing my high KH values.

    I have operated planted low tech tanks for years with out too much probelms.
    I know what to expect and how to fix most any problem but this has me stumped.

    I moved recently and my tap water turns out has a very high KH value.
    I did not realize this when I set up my 55 gal tank at first and planted it.
    All went well at first but I could not get the PH down and soon all the plants died.

    Here are the values of my tap water
    GH 30 ppm
    KH 300+ ppm off the top of the scale
    PH 8.5 It always returns to this value and will never stay down at 7.0.

    Now they way I understand it carbonate hardness is also called temporary hardness because it can be removed by boiling.
    So I tried to boil my tap water. After 30 minutes rolling boil KH still measures 300+ ppm GH, still 30 ppm. I had someone test my water KH and he said the KH value was 680 ppm. Not sure how reliable that test was though.
    That is what has me stumped. What is in my tap water that can not be removed by boiling that is causing the KH values to remain stubornly high?
    I also have a water softner on my home water supply and that does nothing to remove this high KH value. But it does get the GH down to around 30 ppm. Without the water softner my GH would be around 450 ppm.

    I am running another 29gal low tech planted tank at my wifes school and a different water source.
    That tank has been running now for 2 years plants and fish are doing great after 2 years.
    That tank has:
    GH 60 ppm
    KH 0 ppm
    PH 6.5

    Both my tanks run at about 3.5 watts per gallon for light 6000K 10 hour duty cycle.

    My home tap water is from a deep well source and has a high limestone mineral content. I am guessing this is what drives up the KH value so high.
    It also fixes the PH at 8.5. I can add lots of PH down to force it down but it comes right back up to 8.5 overnight.
    Again boiling it does nothing to the KH value. I guess my only fix would be a RO unit to solve my water problem.
    Has anyone else run into an issue like this?
    I would like another option other than an RO unit if possible to lower the KH value of my tap water.
  2. ryanr

    ryanrModeratorModerator Member

    Hi, welcome to fishlore :;hi2

    I wish I had better solutions for you, but generally RO (and preferably RODI) or distilled water are your best bets. You could also try using a standard home tap water filter, just to see if it makes a difference.

    Peat moss can help, but at those levels, I doubt it would be effective :(

    Here's an old fishlore thread I found:

    I also wouldn't bother with pH additives, they won't fix your problem. KH is called temporary hardness because it diminishes over time. KH 'buffers' your water and maintains pH levels, but overtime, the levels reduce as the buffer is 'consumed'

    Another option could be to get a big air pump/stone, and run it in a bucket of your water for 24 hours and see what happens. Strong surface agitation is known to reduce KH - I haven't tried this, but the principles/chemistry logic behind it is sound.

    Good luck!
  3. iZaO JnrWell Known MemberMember

    Are you sure your test kit is functional? GH is a measure of KH AND other electrolytes, so GH is always the same or more than KH...

    As for how to lower your KH, the only truly successful way people have done it is by mixing it with RO water. If you aren't keen on getting one installed, buying distilled water (with a low TDS measure on the info label) can also work. I must say though, with a 55g, the distilled water is an expensive venture over a long time period. A RO unit just gives the owner so much more freedom. Best investment i have made for my fish tanks IMO, both fresh and salt.

    Here is a thread i wrote on detailed water chem that may help you understand a bit.

    As for why your measures are high, limestone will definetely be the culprit, and unfortunately there is no easy way to remove it, hence why mixing it with other water is the only viable option.

    Lastly, please check your test kits as i said. Often this is the first problem. Seeing as someone else tested your KH, i would suspect your GH kit as faulty. But this is something you need to investigate.

    As for your other options, peat, almond leaves and driftwood may be recommended, but IMO that is a solution that simply wont work. All you will be doing is saturating your water with pH lowering minerals without altering your KH. This leaves you in danger of a sudden pH spike

  4. OP

    danhammondNew MemberMember

    Thanks Guys for your responses. I know my tank is buffered to a ph of 8.5. That is because of the high KH value.
    I have three different test kits. My water tests out the same on all three kits. All max out the KH value at 300+ ppm.
    So I started a 50% water change with my other source water that has a KH value of zero. The same water I use in my wife's school tank.
    That tank is also a low tech planted tank and has been doing fine for two years. Plants and fish.

    So I do a 50% water change with this water from this source and I get a 40% fish kill within minutes.
    I test my water.
    ammonia zero
    nitrites zero
    nitrates zero
    KH seems a little lower maybe about 260 ppm.
    GH 45 ppm
    Ph 8.5
    temp 76F

    Temp and ph remain the same both before and after the 50% water change.
    Only difference was the KH came down how much I am not sure because the original reading was off the scale.
    GH went up slightly. Something reacted badly that I am not measuring and killed the fish.
    Note I use this tap water all the time to top off my wife's tank with no adverse effects in 2 years.
    How ever my wife's tank has 0 KH value and a PH of 6.5. This tap water has a ph of 8.2 and a kh of zero.
    Why did it kill so many fish? No idea. These 2 waters are very incompatible with each other it seems.

    Worse I did not realy change my KH value much. I would like to get it down to about 100 ppm.
    The tank only had platys in it so not a big loss and they are pretty tough fish to boot.
    I wonder what killed them? Again 3 test kits all test the same for all of the above.

    I would like to know what is in my water that is causing this. As Izao says my GH should be higher than the KH and I thought so as well.
    But it is not. And I can not boil this KH out of my tap water either. So I doubt it works like normal KH does in that I doubt it will get used up over time either.
    It must be some chemical that causes a high KH.

  5. iZaO JnrWell Known MemberMember

    If you can just get 10 - 20 % of RO water or distilled water for each water change then you should be fine. Again, i still think something is up with one of the test kits.

    Anyway, do you use any chemicals in your tank?

    As for your wife's water, a kH of zero will eventually result in a huge loss of pH hence why the ph in the tank is so different to the tap water.
  6. catsma_97504Fishlore LegendMember

    Try using peat in the filter. It helps and will last several weeks before needing replacement. Use a media bag as peat can be a pain.

    What test kit are you using? Are you sure it is good and not expired?
  7. iZaO JnrWell Known MemberMember

    Peat is an option but like i said, a temporary one unfortunately.
  8. OP

    danhammondNew MemberMember

    Well I tried a test on my wife's 29 gal tank. I added 1 gal of my home tap water to it.
    Her tank before:
    GH 60 ppm
    KH 0 ppm
    PH 6.5

    After adding 1 gal of my tap water:
    GH 60 ppm
    KH 40 ppm
    PH 7.0

    I have never tested her tank at night when the light is off.
    It is a low tech heavily planted tank with no water changes in 2 years.
    We only top it off. It seems perfect to me now. The 40 KH value seems to buffer it to a ph of 7.0 as I would expect it to.
    But 1 gal out of 29 gal tank has that much effect! Wow what is in my home tap water?
    At that ratio in my home 55 gal tank it would only take about 3 gallons of my home tap water to 52 gallons of her tap water
    to get my home tank to a KH value of about 100 ppm. Or about 3 more 50% water changes with her tap water to my home tank.

    Some of you wonder about my test kits. I use the same test kits on both tanks. I have an API chemical test kit with lot numbers and is good for another 2 years yet.
    Also have API test strips and mardel test strips. All 3 kits give me the same numbers in each seperate tank. And the numbers are different between the two tanks. So I know they are working.

    My home tank was setup and operated by me exactly the same as my wife's tank at her classroom at school. I operate and maintain them both. Hers is in excellent condition. My home tank all the plants died last October and I have done nothing to it since except to it off. I am trying to reestablish it now so I can replant it.
    My goal is to first establish a KH value of 100 ppm. Then see if I can get it to buffer at a PH near 7. I am guessing right now I will have to do 3 more 50% water changes with the tap water from my wife's school. Based upon my test with her tank. I am not using any chemicals in my home tank in over 6 months.

    My goal is low tech heavily planted no water change needed tanks. It has worked for 2 years on my wifes tank I should note.
    Her tank has no algae growth either.

    The thing that has me confused is that the KH of my home water does not act like typical KH in that I can not boil it away.
    Yet it did buffer my wifes tank when I added some to it. The real test will be if her tank uses it up over time or not? It should use it up.
    But what if it does not? Then you guys tell me my test kit is bonkers. Well then explain why I can not boil the KH out of my tap water?
    Explain why my test kit measured 0 KH in my wife's tank.
    Explain why my test kit measured an increase to 40 ppm KH after my test with my wife's tank.
    Same kits measures KH off the chart on my home tank and my home tap water 300+.
    By the way my home tank is back up to 300+ KH value now just tested it again. Off the chart.
    Both tanks have the same substrate same filter types same everything except the water.
  9. iZaO JnrWell Known MemberMember

    Sometimes there are bad batches of test kits, so while the test might say it is valid for another 2 years, it might not be. IT's happened before and thats what i mean about faulty. i didnt mean expired.
  10. ryanr

    ryanrModeratorModerator Member

    Sorry for the losses.

    I would think this is osmotic shock that killed the fish. 50% is a very large amount of water to change with drastically different parameters. Even though the pH didn't change (a result of the high KH), the water parameters will have been different.

    What water conditioner did you use?

    I still think you can get these values down with water changes using the same water used for your wife's tank, but I would do it gradually, maybe 5-10% every other day.
  11. OP

    danhammondNew MemberMember

    Yes but 3 different test kits give the same values for each test if one was bad it would show up as a different value than the other 2 tests.
    All three kits are in aggreement with each other on the values they give me for every test I do. And most of my results are as expected.
    So again I am stumped on what is in my home tap water that gives such a high KH reading but does not boil out?
    I know carbonate hardness is temporary and will get used up. But for some reason what ever is in my home tap water does not seem to get used up and yet it does give a high effective KH reading. What can do that? That is why I came to the forum for an answer to my question and what I can do about it other than RO water.
    I am thinking I can blend the two different tap waters to get a good quality aqarium water. My tests are ongoing. But in the end I would still like to know what is in my home tap water?
  12. OP

    danhammondNew MemberMember

    No water conditioner. I am keeping things as simple as possible for the time being. No chemicals at all. The playts will repopulate fast enough anyway. I constantly have batches of young. I have about 12 platys left alive in the 55 gal tank right now. I do have seachem neutral regulator a 7.0 buffer to add to the tank but I will hold off on adding any until I get the KH value down. I doubt that stuff will have any effect on my ph right now even if I add it to the tank.

    I have been using it on my wife's tank and her tank would hold at a ph of 6.5. I could not get it higher until I added 1 gal of my home tap water to her tank.
    See above posts for results.
  13. ryanr

    ryanrModeratorModerator Member

    OK, consider this cat dead (curiosity got the better of me)

    I did some googling, and found a topic at the plantedtank forum regarding reducing KH. There is a discussion regarding the use of muriatic acid and aeration. It gets a little scientific, but from the quick skim I did of the thread, it looks plausible  

    Please be very careful with this - I have never tried it, I do not know if it works - it may be a topic for discussion in the FW Advanced Topics forum here at fishlore ;)

    Hope that helps!
  14. OP

    danhammondNew MemberMember

    Ok I dosed the 55 gal home tank with amquel plus standard dosage. And no measurable effect. I qualify it that way because my actual KH value is off the chart 300+ppm range.
    So if amquel had an effect I cannot tell as it did not drop the KH levels down into a measurable range. The guy in the other thread said he was getting about an 80 ppm drop in KH with using amquel plus. If my levels are at 680 ppm(?) well I would need more than a 400 ppm drop before I could measure a change with my test kits. Again I had a university test my tap water KH levels and that is what they said they are 680 ppm. I can only measure to 300 ppm and below. I am going to do another 50% water change Saturday. I suspect my saturated substrate with high KH will continue to raise KH levels after a water change. So while I might see a short term drop a day later it will probably rise somewhat as the substrate releases its stored KH into the water. When I did the last 50% water change I did notice the fish that did survive the water change huged the bottom probably the substrate kept the water quality near the bottom similar to what was previously in the tank. I will review the muriatic acid thread and thanks for that reference.
  15. OP

    danhammondNew MemberMember

    Hmm Now I understand what went wrong with my pool. I had the same problems. Well I no longer operate a pool. And I can get free source 0 kh water. So as long as that holds out I am not going to use his h2so4 method. Besides my tap kh values are 3 times higher than his are.
    Last edited: Apr 13, 2012
  16. ryanr

    ryanrModeratorModerator Member

    Oh, BINGO - Amquel + and KH, There was a recent thread, and I've searched trying to find it, that was talking about whacky readings of KH and pH with Amquel+. IIRC it was more about Amquel+ consuming the KH, but there was a definite effect.
  17. toosie

    toosieWell Known MemberMember

    With water parameters being so widely different between your home water and the water at your wife's school another 50% water change will kill more stock. There is just too much variance. A pH swing can kill stock but what is actually even worse is a sudden change in minerals. When a water source is used that doesn't contain the needed amount of electrolytes it throws the fish's osmotic functions out of wack. Fish can become accustomed to all sorts of different water compositions and they can even become accustomed over a period of time to water lacking in a proper amount of electrolytes, but if you try to introduce new fish into the tank with few electrolytes, chances are they will not be able to adapt and will die in a relatively short period of time.

    Have you tested the water at your wife's school for GH/KH from the tap, or just from the tank? The fact that the tank has no KH does not surprise me. It is a planted tank that hasn't had water changes done on it in the past two years, only water top offs. Plants use KH as a source of carbon especially when no other carbon source is being made available to them. Any KH that does exist in the school water will be consumed by the plants. A KH of 0 is really not a good situation. The plants will be lacking in a carbon source, and there is nothing to buffer pH except for your pH altering chemical. This isn't good for the fish or the plants, even if they have done alright for the past 2 years.

    The tank at school is likely suffering from Old Tank Syndrome on top of the lack of minerals, and what causes Old Tank Syndrome is the slow depletion of important minerals. If you did a 50% water change on your wifes tank, using the water source at her school, even though it is the same source water you use to top off the tank, a large amount of fish occupying the tank would likely die because there would be a sudden influx of minerals into the tank that have been consumed by the plants, fish and acids that have developed in the tank over the past 2 years. If you chose to take one of your platy over to your wife's tank, the odds are it would not be able to survive. This would all be caused from the lack of available minerals involved in Old Tank Syndrome.

    Our fish tanks require there to be a certain amount of KH. 0 KH is just not good. 0 KH leaves pH vulnerable to sudden deadly drops because there is nothing buffering it or protecting it from the acids that naturally accumulate in a fish tank. The pH in this tank could easily plummet below anything in this aquarium could survive unless you are supremely good at artificially keeping the pH stable. It's a time bomb waiting to happen.

    If the water from the tap at your wife's school actually tests 0 KH, this water would be best blended with some from your home to provide a more stable environment for the plants, fish and pH. If the water doesn't test at 0 KH from the tap, there may not be a need to blend it, but several SMALL frequent water changes should be performed on this tank to bring it out of Old Tank Syndrome without harming the occupants then water changes would be able to be increased in volume and done once a week.

    If the water at her school does have a lower mineral content than your own, blending your water with hers would help with your tank. If it turns out she does have a good amount of minerals in that water but a lot lower than your own, you could just use that water for water changes. Either way, the fish need to be given time to adapt to the different mineral composition by doing several SMALL frequent water changes to prevent them going into osmotic shock, and then slowly increase the water change amount.

    There is really no way of getting around your abundance of KH in your tap water. KH can be removed by boiling BUT the more KH is present the longer the water would need to be boiled. With too much KH by the time you managed to remove enough by boiling you may only have a teaspoon of water left from an entire pot of water, that would actually test as a low KH because it's not something that will boil out quickly enough. In other words, for your water source, boiling just would not be a feasible solution. Total hardness content would also drastically increase because Total Hardness, (slightly different again from GH because it measures more than just calcium and magnesium content which is what makes up GH) would drastically increase!

    So, to sum up... it's not the water combination that was deadly for your fish. When you buy fish you usually put them through some sort of acclimation process to help them adapt to the different water. If your water was close to being the same as the store you bought them from and you just dumped them into the tank, they would likely survive, but if the water was too different, they would likely die. It's the same principle.

    The use of pH altering chemicals is also not usually a good idea. They have to fight against the natural KH of the water to try to keep the pH where you want it, and this puts the pH on a teetering edge all of the time.

    EDIT: It is important to use a water conditioner. It will remove Chlorine and Chloramines if you are on a town or city water supply and it will also neutralize heavy metals that may be present whether you are on a city water supply or have your own well that isn't being treated with Chlorine or Chloramine. Any of these things can be harmful to your fish and plants.
    Last edited: Apr 13, 2012
  18. OP

    danhammondNew MemberMember

    Thanks toosie, I am aware of all that you posted already. My wife's tap water source is indeed 0 kh. Her tank is being treated with a mineral additive and excel for the plants. But I forgot about the kh requirement. I suspect that is why the plants have been slow on the uptake of nitrates. I already added 1 gallon of my home tap water to her tank and boosted the kh to 40 ppm. The ph responded as well went from 6.5 to 7.0. The nitrate level is dropping now so all is well. Plants and fish are doing well.
    Tank looks great after two years so do the fish. No sick fish ever no dead plants all levels are within normal ranges. The balance is not hard to maintain IMHO if you work up to it. The no water change planted tank works best if you start with more plants and less light and less fertilizer than needed. That way the eco system never gets ahead of itself. Then you add slowly and observe changes and write them down. Adjust for your environment and continue to observe the changes. I have been operating it for 2 years without any kh and the main problem was low ph and slow plant growth. But no algae buildup because I did not have too much light and I did not have excesive fertilizer. Now that the kh is up to 40 ppm I expect the tank will see more growth and the ph is running near 7 now and the nitrate levels are dropping. I may have to add nitrates even in a fertilizer if it gets too low. My wife's tap water has a 60ppm GH for mineral as well and the top offs have always added more minerals to the tank.
    I am not worried about her tank at all. I am going to monitor it for a while at this level then maybe push it up to a kh of 80ppm. By the way the excel does add some kh to her tank but I am only dosing 1 capful per week for a 29 gal tank so the plants have had some kh to work with but not a whole lot. At least not enough to measure with my test kit.

    My home tank is the issue. I want to get it planted but first I need to control the ph and to do that I need to get the alky (KH) content down to something managable.
    My goal is 100ppm. My home tank is buffered to a ph of 8.5 right now because of the high kh currently above 300ppm. I can drop the ph but it climbs right back to 8.5 the next day. Plants will not live in that environment. All I have in that tank at this time is substrate and 12 platys. I run 2 filters on both tanks. A hang on the back filter and a canister filter. In my experience that is the best of both worlds. The hang on filter gets the best bio load working. The canister filter is best when chemical filtration is wanted something that is hard to do with the hang on the back type. Plus the water movement is much better with both filters running.
  19. iZaO JnrWell Known MemberMember

    Well Toosie covered almost everything so the only thing i would say is you mentioned trying to lower the pH, which i wouldnt recommend. The only safe way to tamper/alter with pH in water is to alter the KH.

    It is also very difficult to aim for a specific number, so i would recommend not getting to fixed on a specific number for KH.

    I agree that running as much filtration on a tank is a great idea provided the fish arent thrown around by the current, but i disagree with you that HOB filters provide the best bio-ground for nitorbacter in an established tank.
  20. catsma_97504Fishlore LegendMember

    If you have an extra filter and an extra tank or even a bucket, I would do some experiments to lower KH without putting fish lives at risk. In this test tank I would try stuffing the filter with peat. In another test I would try using plain old tea bags. Even set up a rain barrel to use this water with a small amount of tap water.

    It may be possible that you can pre-treat water. But if all tests fail then purchase an RO/DI filtration system.

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