I've lost a couple of clownfish lately and have only found one thing their deaths have in common. Both occurred within an hour of cleaning my screen. A couple of weeks ago, I cleaned the screen, rinsed it, and started it back up. My adult Occ. clown started swimming erratically and eventually swan under a rock and died. I had owned it for a year and a half (4 months in this tank). A few days ago, I picked up a juvi Clarkii in hopes that it would find a home in my Malu anemone (my Occ would have nothing to do with it). It went straight to the nem and seemed happy and healthy. Today I cleaned the screen. Upon restarting it, the clown started swimming erratically all over the tank (hadn't been 6 inches from the nem before this). Within 20 minutes it had swam under a rock and passed.
The tank is a 40 breeder with a 20 long sump. The screen is about 10x10 and is fed off of the return pump. I leave the powerheads in the tank running while I have the return pump off cleaning the screen. Lighting is two 23w cf lights on each side of the screen. It has been running since Feb. and the gha is finally starting to fill in. The only other fish in the tank are a Mandarin and a Randalli Goby (along with his tiger pistol). The tank also has a handful of soft and lps corals. Everything else seems to be fine.
Any ideas as to what is going on? Could cleaning the screen be releasing something toxic? Maybe the rinse before putting it back into service? Any ideas are appreciated. Thanks.