Landmeier, if you wanted a dwarf lion and a trigger then you would need at least a 55gal. That is if you got one of the smaller triggers. Some get rather large and would need at least a 75 gal. Even then if full grown may need a 100gal. Anyways, a smaller type trigger such as a picasso,bursa, or crosshatch and a dwarf lion would fit in a 55gal together. Any mixture but no more than two I'd say. Perhaps three? I personally don't mix triggers and lions together due to difference in temperment, but many have success with it. I just don't think a lion is happy with a trigger in the same water. Not that I haven't tried it (cuz I have), just won't do it again. HTH and just my 2cents.