Ginny you are the queen of Aerotanks! For me it's about 3-5 depending. The kanger sub tank mini and nano are always in rotation. I got a used v1 Atlantis that is also usually in rotation, my Aerotank v2 is still in rotation and I just got an Aerotank turbo I'm thinking of taking out of rotation-trade or sell, thing is burnt hits galore.