Thanks...I just set up the tank 3 weeks ago, so I guess it wouldn't be wise from the fishes' point of view to take them out, put them back in their bowls for a few days and take care of the silicone just for a cosmetic issue. Boy...leave it to a newbie to ruin a new tank! I just bought a new med., Kanacyn, that is a white powder and you can't even tell it's in there. I don't think I'll use the Bettamax again. I can tell the fish really don't like the dark green water either. They lie on the bottom and "pout"! Don't blame them, I guess!
Anyway, thanks again, and if I tear down the tank someday I'll try to get the stain off. But, I suppose, a stained silicone strip is better than sick fish!