I don't believe anybody's pa****er hs 80ppm NO3. I do believe,
from observation, hobby NO3 testkits are not accurate.

It's my guess that this problem is more to do with old
tank syndrome than anythig else, that is a pH shift up
makes the small amounts of ammonia in the currently acidified
water turn very toxic.

--
Need Mercedes parts ? - http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
1970 280SE, 72 280SE | Home page: http://rs79.vrx.net
633CSi 250SE/C 300SD | http://aquaria.net http://killi.net