Tyrosinase & Barry N.
Thanks for the advice. I don't know what could have triggered a stress response. The tank is very stable. ph runs at 8.3 to 8.1, NO3, NO4 & NH3 +4 are undetectable. I also run carbon all the time and ozone on a controller with an orp of 380. Orp started at 265 Thursday 1/12 and I have been increasing it slightly, daily since then.
The ozone is a new addition over the past 2 weeks. Could the change in orp have triggered the response?