That 'cubic' theory is very interesting. Although it may be a little difficult to estimate the cubic inch of fish since the geometry is not symmetric.
Tank size is important to whether your tank is overstocked or not. But, I do see one fish that will get too big for anything less than a 75g, and that's the pleco. Plecos can get over 18'' in length and should grow fast if given the proper conditions.Ok, people have told me that my tank is overstocked. But when I had less fish in my smaller tank(2 1/2 gallons) they were unhappy. If you do have neon tetras what is a good rule of thumb. I tried the link above, but being a newbie, it really confused me. This is what I have...1 small Africain Dwarf frog (about 3/4 of an inch), 1 placostamus About 1 1/2 in.,2 spotted cories about 1/2 in., 3 neon tetras,1 spotted tetra , 1 tetra of some kind (1/2 inch). Until I put the 2nd spotted cori and 2 more tetras in the tank, the tetras I had would nevr "light up",now they are always bright. They look as if they have plenty of room