Irrelevant But Interesting Question About Ph,kh, And Plants.

Discussion in 'Aquarium Water' started by FishyGlenda, May 19, 2019.

  1. FishyGlenda Valued Member Member

    I’m a beginner in the aquarium world and just started doing some research on KH/GH/PH. After learning about it and looking at it in a chemical perspective, I thought about a somewhat irrelevant but interesting question: When the ammonia gets converted Into nitrates, the pH goes down due to the acidic nature of nitrates and we all know that we can lower a pH by adding something more acidic to it. Vice versa. But The KH in your aquarium prevents the pH from going down by neutralizing all the nitrates until it’s completely used up. And when it’s completely used up, that’s when your pH starts to go down. Since plants consume the nitrates produced, does that mean the plants in a planted aquarium can act as a buffer just as KH making the KH last longer as well? I believe the nitrates would have a smaller impact in the pH in a planted aquarium because the nitrates would be getting neutralized not only by KH but they would also be getting consumed by the plants preventing them from staying in the water and making it more acidic. In return, the KH would also last longer because now the plants are helping with the nitrates too by consuming them. Am I right? In other words, does having a planted aquarium make your KH more durable and your pH more stable than having a non-planted tank due to the plants consuming the nitrates? I just thought this was a cool and interesting question. I tried googling this question but didn’t find an answer.

    Oh. And I know that carbon dioxide gets consumed by plants making the water less acidic and raising its pH. But this question is about the plants acting as a buffee just like Kh does meaning that it does not lower or rise the pH but keeps it stable since it would be preventing the nitrates from affecting the pH by consuming them.

    Last edited: May 19, 2019
  2. toosie Fishlore VIP Member

    Nitrates themselves are not acidic. However, there are acids produced during the nitrification process.

    KH absorbs and neutralizes acids (not nitrates) but pH can become unstable if/when KH gets too low (often below 3 dkh), but generally higher KH levels can suggest higher pH and lower KH levels can suggest lower pH levels...but other factors can come into play, so even this isn't always true. KH doesn't have to be ALL used up for pH to go down, but a 0 KH can lead to a pH crash but pH can be 6.0 or lower before KH is 0.

    Plants do use nitrates but they do not use acids, so being as nitrates are not acids, the plants will not help KH last longer. In fact, plants will use KH as a carbon source if another source of carbon isn't provided for them. And interestingly enough, our nitrifying bacteria also use KH as a carbon source.

    Having plants tends to make pH fluctuate more than in an unplanted tank, due to the fact that they give off CO2 at night, lowering the pH, and then reverse the process to give off oxygen and use the CO2 during the day, increasing pH over the course of the day.

    Hopefully I haven't missed any of your questions, fellow water geek. ;)

  3. Basil Well Known Member Member

    And in the same vein, I’ve been pondering using coral to raise KH.
    My LFS store recommends breaking up whole coral and adding it to the filter in a media bag. LFS gal states that keeps her tanks at a 7 ph.
    It makes sense as the carbonate would bind the hydrogen until it was in a neutral state.
    But I’ve also read that coral is used to raise ph versus just keeping it neutral. Although I would ideally love a higher KH in my tanks I don’t want it with a ph of 8+. So I’m not sure of the chemistry behind it.

    Last edited: May 19, 2019
  4. wintermute Valued Member Member

    When I was keeping goldfish I was constantly battling dropping PH. The tap water I was using had a PH around 7.6 - 8.0 or higher, but I struggled to keep the PH above 7. I added some crushed coral to my filter, and before too long the tank was stable at a PH around 7.5. I have some difficulty measuring the exact PH as my test kit has a low range test and a high range test that overlap, but the low range test always reads as 7.6 and the high range test always reads as 7.4 so my guess is it is 7.5.

    Now I'm keeping tropical fish that prefer a lower ph, but they seem to be doing well in the PH 7.5 water, and I'd rather it be stable than constantly changing. The LFS water is around the same PH as mine, so the fish are already aclimated to that.

    Interestingly I have a rainwater tank, and the water in that is around 6.5 ph I have a carbon filter to allow me to use it for water changes, and I tried for a while using that water mixed with tap water (which gives me a PH around 7) but even after enough water changes to have changed the entire volume of the tank three times, the PH is rock steady, and has not dropped from the estimated 7.5.

    So from my anecdotal experience, crushed coral works really well at stabalizing your PH, in my case at somewhere around 7.5 (which I thought was because of the source water, but now I'm not so sure). I put maybe a handful or two of crushed coral in the filter a couple of years ago, but most of it is actually gone now (I guess if the PH starts to drop it is a sign for me that it's time to get some more).

  5. Basil Well Known Member Member

    Thanks Tony!
    When I’m finished with my quarantine tank, I may start experimenting with that tank and add the coral, only use the RO with equilibrium and see what happens!
    I’m keeping my display tanks stable at 7.6/7.4 with the seachem buffers (I get the same readings as you with the kit. Need to calibrate that ph meter I purchased lol!) so it’s good for now. And I don’t want to screw them up!
    But if would be nice to only have to add equilibrium to the RO water.
    Last edited: May 19, 2019
  6. toosie Fishlore VIP Member

    KH is a measurement for carbonates and bicarbonate hardness. Often calcium carbonate plays a big part in that. Crushed coral leaches calcium carbonate. The amount of leaching (and how quickly it leaches) in part depends on how much is used, the acidity of the water, and water flow. But as the calcium carbonate leaches into the water, hydrogen ions shift to hydroxide ions (which are always in a ratio together to determine pH) thus increasing pH. So, crushed coral not only increases KH, but it also increases pH as a result. And if you use enough crushed coral, it can raise your pH to about 8.2. But by using little bits, the acids that act as an opposing buffering system, help keep pH down. If one force overpowers the other, the pH will shift accordingly. So for this reason, I like to test KH and pH to monitor and determine affects...adding more or using less crushed coral for desired affects. However, I do always recommend using CC to obtain a healthy KH and allow pH to be what it wants to be.
    Although soft water (determined by GH or general hardness) often has a lower pH, it can surprisingly at times have a higher pH than might be expected, because of a higher carbonate hardness or other possible pH buffers (carbonate hardness being only one). But it is often how many minerals are in the water, available to the fish that determine how well fish do in a type of water, than the pH. A soft water fish can adapt easier to harder water and higher pH conditions, than a hard water fish can adapt to softer water (fewer available minerals) and a lower pH. But because pH isn't always the same even if two water hardnesses are the same, it is more important the pH is stable than at a certain level, as long as adequate minerals are being supplied.
  7. Basil Well Known Member Member

    Thank you @toosie! That’s exactly the chemistry lesson I was looking for!
  8. wintermute Valued Member Member

    Thanks toosie, I haven't tested the GH & KH for a while I should do so. When I had the goldfish, for a while I was using RO water (but not adding anything) and that was a disaster! Changing to tap water didn't help a lot but was better than RO. The addition of the crushed coral was the best thing I ever did. Got rid of a lot of stress for the fish, and for me!

    I've started using start right B which was recommended by the LFS, It's salt as far as I know, but not just sea salt. I should do some tests in a bucket of water to see what the effects of it are as well.

  9. toosie Fishlore VIP Member

    You are both very welcome.

    RO works well if it is remineralized and buffered properly, but yes, otherwise it can be a devastating nightmare, so I totally get what you are saying. The crushed coral can certainly be helpful when KH is lacking. It does also increase GH, but I wouldn't solely depend on crushed coral to remineralize RO water, simply due to the fact I don't feel it adds all of the elements fish require. As a supplement such as you describe to add to your tap water, is a good use for crushed coral.

    Most freshwater fish do not require ... and some even don't do real well with salt. But testing it will certainly let you see the effects it has on the water, but nothing in our freshwater aquariums use salt, so the salinity can increase over time due to evaporation if top ups aren't done with unsalted freshwater before water changes. Maybe this product does add something other than sodium, so I like the idea of testing, but it should give some indication of what's in it on the container?

    Anyways, I'm a feared we may have done a little hijacking of @FishyGlenda's thread, so I'd like to apologize to her for that, but if either of you would like to discuss anything more, perhaps it would be best to start a new thread, and if you @toosie me, I'll be happy to join you there. :)
  10. wintermute Valued Member Member

    woops, only been here two days and already threadjacking :shy: Sorry FishyGlenda!

  11. Basil Well Known Member Member

    At least we are pretty much staying on topic lol!