Last week when I tested my water chemistry, my pH was about 8.0. Ammonia was at 0.25 ppm, nitrite was at 0.25 ppm, and nitrate was about 40 ppm.
So the past week I added 1-2 tablespoons of 'pH down' morning and night, testing the pH as I went. (Didn't bother doing all the tests each day, since the ammonia-nitrite-nitrate series of tests take about 10 minutes to complete, whereas pH is immediate.)
Happily, I've gotten my pH down to 6.6.
Unhappily, my nitrite and nitrate have shot up.
Happily, the remedy for high nitrate is to plant more plants. So here are the new additions:
Next project: finish enclosing the ends of the greenhouse...