I normally do clean the tank with soap and water every week, I will try the bleach and alcohol trick! maybe that's what I'm missing. I'll close up the holes letting light in, although I'm still using the internal air pump, guess I'm picking up a better one and air stones today! (I was planning on it but holding off as long as possible. for what reason? idk hehe) Thanks guys! I'll let you know how it works out.
Make sure you rinse the stuff you're putting back into it thoroughly because if you don't you're just going to reinfect it. Alcohol? I don't know. I like to drink mine.