Trouble with low pH
About two months ago I started my first Walstad style tank. I used 1 inch of miracle gro and added 1 inch of black sand on top, and I've added a variety of plants such as rotala rotundifolia, cryptocoryne wendtii, bacopa caroliniana, and pearlweed, as well as salvinia minima at the surface. Everything has been going pretty smoothly. The tank stabilized a bit about two weeks ago, and I've had good growth with everything and added some snails. I'd like to add some amano shrimp I have from another tank, but I'm hesitant to do so.
My water from the tap has a pH of 7. The other tank with the shrimp has a pH of 7.6, probably due to the crushed coral that has been sitting in the filter. The planted tank I've been working on, however, has a pH of 6.0, if not lower. I feel like such a change would probably hurt my shrimp, so I've been very hesitant to move them.
I've added some crushed coral to this tank, too, and yet the pH has stayed the same. It only ever rises to 6.4 if I perform a 20 - 30% water change, but the day after it falls back down to 6 (that's the minimum on the API test kit). There are a few things I can think of: 1) this tank doesn't have a filter, and the crushed coral sits on the substrate. With that being the case, I assume that it doesn't dissolve and release minerals as quickly as crushed coral that's in circulating water in the filter, therefore not buffering the water. 2) The lack of circulation is inhibiting gas exchange, allowing for co2 to be expelled from the water at a much slower rate than if there ample water agitation, causing the pH to remain low.
I was looking to not add a filter because I wanted to go the Walstad route completely and also not deal with more frequent evaporation from the filter. Is implementing a filter the only solution, or is there something else I can do?
Last edited by Ve20; 11-02-2020 at 02:53 PM.
Reason: Extra info