yeah I honestly doubt it's a water chemistry issue. the other fish are fine, and there are tons of shrimp and snails in that tank that are fine as well. and i moved him to an established quarantine tank that's had a steady bioload (1 molly, 1 danio), and i havent seen any improvement in the 18 hours he's been there. could it be a swim bladder issue? he wont eat, so i get any peas into him.
