Inch per gallon is useless IMO. As far as inverts having a low bioload I don't think snails shold be included there, especially briggs/diffusa they have a rather large bioload.Neons seem pretty low, even for their tiny size, but you could probably do easily twice the inch per gallon "rule" with neons. That rule seems to work best with about 3-4" fish IMO, smaller than that, and you can stock more inches, larger, and you can stock less inches.