hello, i am sorry to ask a possibly dumb question, but my fish always seem to act like they are starving when i come into the room. is this just my thoughts. i also am getting some brown (what i think is diatom) algae on the sand bed. i think i may be slightly over feeding ( twice daily) it doesnt seem like much that i am giving them and i do have about 50 crabs and about 20 snails for a clean up crew. oh, my tank is 150 gallons, do i need more of the crew. also i see so many differtent types of snails. is one better than the other. thanks for any help.