Only one tank set up. I have one that one day might get plumbed in as a prop tank and another that I am going to set up simply to quarantine the animals. I heard someone talk last year about zoanthis pest and even though they were not my cup of tea at the time I picked up some good information.
SO 1 tank now but might have 3 be the time this is all over
Five and am about to add to the fun with several large tubs to replace my sumps and fuges and will add a frag tank (have 7 tanks right now if you count sumps and fuges, but I usually don't).
I have 0 running right now but I have a 30g Oceanic cube as my display and a 20g QT that I'm in the process of setting up. They will be running in about a month.