I was getting some furry grey-green algae on my plants, none on the glass, and bought some ghost shrimp yesterday. They scattered under the mopani log for most of the day but when I got up this morning it looked like a lot of the algae was gone and the shrimp tummies looked the color of the algae. They are still under the log, venturing out periodically, but staying on the gravel. So, do they eat at night and are they pretty good algae eaters? I have read pros and cons on the net.