My opinion is a bit different than OG's, all except for the fact that they are more than willing to munch on any fry that are available!
I had seven of them in my planted 20 gallon tank and have two left. They have all been very active in my tank. I have really enjoyed their addition. Feeding time is pretty funny, too, since they are very determined to get some food, even to the point of swimming upside down along the water surface, or sometimes crawling over other fish to get a bit!
They are excellent at cleaning up the tank, and while mine don't eat anywhere near the amount of algae that my Ottos do, they still are constantly crawling over every surface of the tank grabbing anything available (including algae!). You don't have to worry about any particular foods to feed them, as they are oppotunistic feeders. Whatever is available, they will happily eat (including fry
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I have never seen anything to suggest them being nocturnal, although they may be even MORE active at night! Mine are at least as active as my Corys all day long!
Other shrimp may be even more delightful to have in your tanks, though.......I just haven't had any others to comment on.