I briefly started to look into this back when Ski posted the question about the larger blower he'd obtained. I couldn't find a site that would relate the HP ratings to either a number of tanks or a number of drops. Knowing what volume of air can be moved at a given pressure is more important. Then the efficiency of the pump can be taken into account to derive what the necessary real world HP.
So what volume can they push? A CFM rating usually isn't too hard to find. Now, finding chart relating volume to pressure, that's a bit harder. Then to find some answers we'll also need the number of tanks, the lengths of the air line(s), the diameter of the airline(s), and the depths of the drops in the tanks. From this we can find the pressure exerted on the blower and the rate of air exiting all of the drops in the tanks.
But at this point I realized, there's a lot of math here and I'm not setting up a blower for myself, so I stopped trying to find the answer. But perhaps this helps give some idea of what to consider if you try crunching the numbers for yourself.
IMO if you have a fishroom, a large linear air pump is a better idea. If you have a fish-basement or a fish-building, then a blower is much more fitting.
