I have about 15 of them in my 37g tank. I will all ways say this, but Amano shrimp are the best hair algae eating shrimp I have ever owned. Females are more bigger then the males in size. They are extremely hard to breed compare to other shrimps. You need almost saltwater to breed these shrimp. All shrimps have a low bioload, so about 4 or 5 would do it. Fair warning, these shrimps do jump out the tank, get a lid or some sort from this happening. I lost about 3 of them, because I take a chance and keep a open top. I love Amano shrimp, they are extremely active little guys. I actually play with them on my fingers. They pretty much eat anything they can find. I feed mine cucumbers twice a week. I also feed them bloodworms when I'm feeding my other fish. Very friendly and harmless little shrimp, so I wouldn't worry. Here's a picture of mine eating cucumbers.