I have a 55 gallon planted tank. because my well water has nitrates in it, I have to use some distilled water (along with some well water) whenever I do a water change. The distilled water has a very high ph. I just keep putting api Down in - and it just won't get past a certain point - I can't get it down to 7.4. It stays around 8.0 and that is with alot of api down.


I tried putting some of that shell substrate into the tank to naturally decrease the ph and that did nothing.


I keep the KH at 6



suggestions for a better product perhaps?

Hi @marshmallow,

The distilled water may have a high pH but any small amount of acid added to it would result in it plunging to very acidic (low pH). It is more likely that your well water that is keeping your pH up along with the shell substrate. Shells are comprised almost entirely of calcium carbonate which has a natural pH of about 9.9. In conditions with a pH lower than 9.9 shells dissolve increasing the pH back toward the 9.9 pH. With shells in the tank the pH will always try to return to alkaline and increase general hardness (dGH) as the shells dissolve.

Here is my suggestion.

1) Continue to use your well water, distilled water combination

2) Lose the shells, if you are trying to lower your pH they will constantly be trying to increase it back.

Why do you want your tank to be more acidic? Is it fish related or plant related?

-Roy

Agree. The shells are alkaline and will raise your pH. Use a neutral substrate, avoiding calcium. Also check the pH of your water mixture in a glass container to see where you are starting from.
Good luck,
Dave

If you want to lower PH, you have to lower KH.

PH down is a light acid it will burn off KH but it is not advisable to add it directly to an aquarium the direction it comes with is a recipe for the slow death of livestock.

I would suggest 1st removing the shells.