Your running 3gallons/fish, id reccomend saving up for atleast a 55/75gallon. And then you could deck it out with rock formations and such, and if you have a creek or river by you look for some floating wood, soak it in warm water, pull of bark and debris then bake 350° for 15 flip over and repeat, makes awesome driftwood!!
But to be productive and answer ur question it depends on the size, i dont see 11 fish utilizing this one formation, maybe try plants on each side?! Fish love decorations and they feel more comfortable and safe thus displaying their natural behavior.
Goodluck!
6 rbp