KH Issues

[TSCECRider6B]

Hey everyone! I having been battling with myself on what is the correct thing to do. I have. 125 gallon discus planted tank with some other fish that go well with discus in it. Also have a 40 gallon goldfish tank. I have been using strait RODI water in it. The first fill was with strait tap water. My water parameters in my discus tank are



Ph - 7.6
Ammonia -0
Nitrite -0
Nitrate -0
Gh -125
Kh -60
High ph -7.4


I have been doing weekly water changes of 23 gallons a week. And the water parameters have not changed other than my KH is becoming lower but not my GH or PH. I understand that my GH and KH should be softer for discus than most. I understand that I should be adding Minerals back into the water before adding strait RODI water in my tanks correct? My concern is that if I do that using a product like Equilibrium that it will make my GH go up. I know that I can use an alkaline buffer to help with my KH but won't that make my PH go up? I am concerned that my KH will continue to drop causing an issue with my PH being unstable. Do I add Acid buffer in the that alkaline buffer to make the ph go to where I want it? I am so lost on what to do. I feel that i may be overthinking all this. There are plants in there so I don’t want my fish or plants to die by using water changes with RODI water. Again i have not been re-mineralizing with anything yet I understand that to be bad. My ideal with by using acid buffer, alkaline buffer, and equilibrium in the RODI water, I can create the perfect water for my plants and discus. Should I do that or just cut tap water with it and then use Prime?. Advice is so needed. I am lost on what to do. I do not want to harm my plants or fish by using the RODI. The reason I am using the RODI is my fish tanks were not doing good with tap and a friend told me RODI is the way to go and so far it has worked great. Everything has been going smooth so far and they seem happy but now my KH value being come low every week is starting to worry me. I am lost on how my PH is still high but my KH is low? How does that work. What is the right thing to do? Thanks so much everyone !

 

[Byron]

All the hype we are bombarded with about buffering/raising the KH to prevent this or that only applies to tanks of fish that have the need for harder water with a basic pH. When you have soft and very soft water species, the GH and KH can be zero and the pH can be acidic. For most of these fish, and certainly discus, the lower all this is, the better.

You could have just RO water and the discus would be happy. I have zero GH/KH and let the pH fall where it likes. As the tank biological system becomes established, the pH tends to settle at "x" and stay there, even with water changes. Stability is the key, and this can occur without KH. Provided again that the fish species are suited. If these fish live in such water in their habitats, and have done so for thousands of years, they are not going to be any different in the aquarium [always a few exceptions, just so someone doesn't fly at me here].

If you are using RO for water changes, it will slowly lower the GH (and KH) and the pH will lower with it.

As for using Equilibrium for plants, don't, given the soft water fish here. I went down this road for a couple years, until a marine biologist asked me point blank just what benefit for the soft water fish I thought this stuff was having. I have not used it since. I do have a calcium deficiency, but I found that Flourish Tabs next to the sword plants solved this issue, and it has been fine for some 7 or 8 years now. Provided you do not have high-requirement plants this will work fine.

Edit. Forgot to mention, use the regular pH, not the high pH, here. It will likely give a more accurate reading, as the two do not test the same.

 

[StevenF]

in my planted RO tank I do use a GH booster in it. I stableized my ph by putting a decorative snail shell in the tank. If the water becomes acidic the shell will dissolve and bring the PH up to 7. Once the PH is 7 the shell stops dissolving. Since I have done that my PH stays very close to a ph 7 +/- 0.3. I have to replace the shell about once a year. But I have very small tank compared to yours. So yo might need something more than ocean snail shell. You could try putting some crushed coral in your filter. crushed coral iand snail shells are mainly made of calcium carbonate and will work.

if use crushed coral to stabilize your PH any that dissolves will put a some GH in and it probably give you a little bit of KH in your water. Again I cannot predict the find aGH and KH. So crushed coral it probably all you need. I would put the crushed scoral i the filter. That way you could remove it from your system if needed. IF you put crushed coral in the substrate of the tank it would be difficult remove.

KH is a measure of CO3 salts in the water. in a natural stream is mainly from calcium and magneisum carbonate. However Most KH boosters are potassium bicarbonate which can push the PH past 8. And water with just potassium can cause poor health in fish and should quickly kill them. High levels of potassium can also kill a human. Natural water always has a little potassium and sodium at around 5 parts per million for each. on Degreee Of KH will is 17.8ppm. That would put a lot of potassium in your water with no sodium. So don't use a KH booster.

Note in the aquarium hobby we also measure GH in degrees. Gh measures only calcium and magnesium in the water. in steams calcium magensium pressent in the form sulfate, chlorides or carbonates. salts. For a soft water stream The GH could be a couple of degrees GH or could be less than 1 degree. But it isver zero. so if you do remineralize target one degree.