Last night i was on looking for help because my large ryukin was acting ill. over the past 24 hours i have slowly dropped the temperature in the tank from 75.9 F to 70.0 F. i did a 25% water change and cleaned out my intake and outake hoses on my 2 fluvals and all the fish are up and about. i couldn't believe the build up of decaying food and poo. but after seeing what it looked like i realize that everytime i turned off the filters for maitenence that i hadn't cleaned those as well, and when i fired the filters back up again a huge puff of that toxic stuff was polluting my fish tank. So my new rule to myself is that that will get done with every filter cleaning. Thanks again for your help fish doc.