what species of Starfish/snail/sand sifter of any sort?

[intarsiabox]

Conchs will do a great job and only go after algae type material including diatoms as far as I know. They work so well in fact that you may end up having to feed them nori or algae pellets for koi. Usually if you see a conch on the glass of your tank it's because they have cleaned up all the algae in your sand and are starving.