I already told you the only thing you can possibly get from treating the tank with Erythromycin is a possible ammonia spike if you have a lot of dying cyano
. Treating the tank with it is no big deal and beats having to deal with cyano
if it advances as you saw what it can end up looking like. Thick sheets of cyano
that will cover everything in your tank except the fish. Doing a blackout usually don't work in the long run as often the cyano
will return. If you use Erythro you don't need to turn off lights and do a black out also. Do one or the other. IMO
the Erythro is the way to go, it's going to kill it so it doesn't come back. But hey, it's your tank so do what you feel comfortable.