21... I can make dinner and have a lil' hatch to slip extras down for the fishys! and most are tall.. not much footprint to them.. I like me a big footprint over anything else. I'de be afraid of going threw the floor of the one underneath... and I like the 3 TVs on the bullnose... think that's a member here's? or maybe I saw it on tv. Most those are SW not fw
And 3 would be awesome on a houseboat in a lake... no need to build a tank.. you live on one.