I'm at 12 Right now, counting the 4 - 10 gallon holding & quarantine tanks, & the 2 dedicated for Tilapia, before I move them outside for summer... still have a 250 gallon to set up ( requires some house work, before installation, & 2 - 30 gallon longs in my built in set up, where most of the other are, that I'll probably use as breeders, when I get time to fill those... I keep pretty busy, between work ( not retired yet ) & all the farm animals we raise outside... & all these tanks inside...