Filter STINKS! Forgot to drain it after stopping it
So my eheim pro 4 canister filter [censored][censored][censored][censored]ing REEKS like a terribly stale sludgy pond. It's hard to describe but I know I've smelled it in nature before. It never smelled when it was running when my tank was up. I'm currently rescaping and dry starting.
The thing is, I've soaked and clean it in vinegar, peroxide and finally bleach... the smell is still hanging around. I'm actually more curious how this happens then how to fully clean it (hence the post in water parameters forum). Did it go fully anaerobic and have nasty bacteria grow or something?