the shrimp will clean and eat many things, they love brine shrimp too, so tehy cna be fed, just in a 58, no more than 2
and an adequate crew will help alot, 58 gal, maybe a half a dozen turbo or trochus snails and an algae eater too(algae blenny), you may have to help some, because some of them will only eat algae under a certain length, but they will do much of the work
diatoms, aren't really a bad thing(or good), just part of the cycle which you wish to complete, so it really is a good sign that you are heading the right direction
jsut make sure your water parameters are in line before adding them
HTH