So would 2 Trop Blumats cover a 45 gallon Smartpots?
I don't think so, I have attached the blumat user guide and if you look at page 8 it says 3 will cover 50cm which is about 19 and a half inches. For pots that deep I think you will want to use the blumat maxi's which is just a longer version of the tropf blumat, see page 11.