Yea thats wat i have...initially the extra height will really just make for more room for waste dispersion, cuz my lion doesnt really move around too much, just kinda perches in his cave and watnot...its still a great tank tho. Those two lions will be fine with a tusk, and the tusk will be fine with the crabs too. Mine doesnt really pay that much attention...just keep him well fed and hell stay away, just toys around with em. But with the extra height, u should try to make some really cool rock structuring (and by the way, u can by a laser lighting unit to put in yer tank, but i think its kinda superficial, so i wouldnt do it personally)