Two months ago I set up a 20 gallon long Walstad tank, which was intended for my Southeast Asian community (Betta + Harlequin Rasboras).
These fish like soft, slightly acidic water, and I was hoping to eventually make it into a dark water / biotope type tank, using botanicals.
Well, this tank has steady 8.0-8.2 pH, even though my tap water is 7.0 (and usually drops to 6.8 or even 6.6 in my other aquarium, where the fish currently are).
Plants are not doing too great in this tank either. Lots of yellowing, holes, misshapen leaves, stunted growth...
Full spectrum LED lights on for 5 hours, off for 4 hours, on for 5 again, then off all night.
Is high pH a common characteristic of Walstad tanks? Is there anything I can do to lower it to a 7-ish?