how many loaches in a 4x2x2?

[libingboy]

how many loaches can i comfortably keep in a 4x2x2 for 2 years, if the largest one is currently 5" and the smallest would be 3"?

[Mark in Vancouver]

Few. You're approach is off if you're thinking of maximizing the population for the space you have. You don't need to do this. Keep a few of any loach in this tank and let them develop. Crowding should be avoided, IMO.

You could fit X number of loaches in a tank that size, but is that really the way you want to keep them? I try to keep my tanks underpopulated if I can. All the better for the small numbers of species I keep in groups. My "big" Botia tank is wanting to expand, I'll admit, but that's renovations, not a holding tank.

Let the ones you have get comfy. That's my advice.