Poor fish, nothing seems to be going right for them these days. I seem to have nixed the algae problem... I still have some hair algae and stuff growing in there, but the antibiotics really did clear up the nasty BGA. Now I have new weirdness in the tank, though:
Cloudy water. WTF? I honesty don't know what's causing this problem. A little interweb research suggests that the main causes of this problem could be diatom blooms, overfeeding, or bacterial blooms (usually from cycling a new tank). I'm definitely not overfeeding (fishies have been down to a once a day feeding schedule since the BGA problem happened), and diatoms seem unlikely given the color of the cloudiness. I'm thinking this must be bacterial then, perhaps a side effect of the antibiotics or something. Maybe my bacterial colonies are reestablishing themselves post-nuking.
The fish are looking fine and don't generally seem to care, but just to make sure I tested all the levels today when I did a water change.
Looks pretty good. The lack of nitrates may eventually be detrimental to my plants, but for now they seem to be doing fine. The water sprite is even showing some new growth, which is very encouraging. I did a 20% water change and a bit of algae removal, but nothing else. I guess I'll sit tight with the cloudiness for a few days and hope it resolves itself.