Within the past few days, I've noticed a small amount of diatom/brown algae growth on the lower parts of the glass and on the sand/crushed coral substrate. My only inverts are my red knob sea star and blood fire shrimp, both are carnivores. What types of snails eat diatoms and how many would make a good crew for a 125g? Also, is this the type of algae that tangs will eat?