About a month ago I bought 3 "algae eating shrimp" and put them in my planted 29 gallon. The next day they had vanished and I didn't see a trace of them till about a week later when I saw bits of shrimp carapace during siphoning. So I assumed they were all dead. Well yesterday I almost completely drained my tank to move the whole set up (painting my room) and I saw all three of the little buggers scurrying around! After refilling the tank, the shrimp vanished. Is there any way to entice them to stay out where I can see them? Should I get them more shrimp to keep the company?