I realize this isn't a very common problem but I'd appreciate any input you all had. In my 90G tank I've been using these cheap hollow ornaments just for the sake of giving the fish some hiding places, but I hadn't stirred the sand beneath them in quite awhile so today as I was doing a water change I took them out because they're a pain to clean and suddenly the worst sulfur smell just hit me. The sand beneath the ornaments was nearly black. I realize this is because of anaerobic bacteria making hydrogen sulfide but what I'm wondering is if I should get all my fish out and into some non smelly water asap? There must've been a lot of trapped gas because It smells horrible, I can barely stand to be in the same room with the tank. None of them are gasping at the surface and I've got two powerheads running to help aerate the tank. I can't find any info on what to do in this situation. Help?