i have a 24 gal nano but i run a 15 gal sump with it a good asm skimmer and a hang on fuge on the sump so it increases the water volume. the only drawback to a nano in my opinion is the smaller the water volume the faster things can go wrong and you are more likely to get temp swings. if you add...
i have a yellow watchman gobi in my nano and he has picked up one small piece of sand in 3 months, so no chance i think of them digging much.
i do have a pistol shrimp though and he does dig lots.
personally i think i would think about the gramma and keep the other two with a gobi, makes for a...
my clowns found a home in the purple mushrooms, the small clown is under one of the mushrooms peeking out. have seen the small clown take frozen mysid shrimp and try to tive it to the mushrooms. talk about dumb :)