Snap. I got it also when I did a rescape. Reason is because disturbing the substrate releases small amounts of ammonia. Took me quite a while to clear totally. Spirogyra thrives in high light so reducing the lighting may help. I cleared mine by lots of water changes and normal dosing excel and also keeping very stable conditions. Rosy barbs will devour it if made hungry.Dave Spencer said:Dagnab it!
It seemed to appear when I did a rescape