Hi, I nearly lost quite a few fish the other day as my congo's were just about swimming (looking like they're about to die) on the gravel and my parrot fish was resting on my bogwood. my peppered corys were also rubbing. The week before i also lost 5 angels and only had one survive. I've now added some methylene blue but i'm unsure if i need to add more than the one treatment as i don't know what the problem was in the first place. It says to add another dose after 4 days but its been 4 days tomorrow and the water is still pretty blue. It's not whitespot. 
