ok maybe they are not "sand fleas" but they are very tiny like a flea and they are green and do not like it when the light is on! When my timer lets my lights on you can see them for about 10 minutes before they hide and there are about 50 of the little buggers!.. you will see them head to a little spot of algae on the glass and seem to be eating it (i have to admit, my algae is really diminishing since we noticed them) although i keep reading i cannot find anything that is like this. does anyone know what they could be and if they are good or bad?... thanks in adavance,,,,, Tammie