I suppose your right Cecil but pushing things to the limit and over crowding can get you exactly where CCF is right now. And can be very hard to get out of it once said fish start to die.... Hope you can break the chain CCF... and figure out what's going on.
RC
Not advocating pushing the limit but you can go quite a bit higher in cc with the right equipment Rainman says.
And just so you know, you were absolutely correct on your rule of thumb for aquariums and I didn't disagree. It's just that although similar, aquariums and recirculating systems have different goals, as do koi ponds which are also basically small scale recirculating systems.
