I bought a pair of Ret. Hillstream Loaches, the male 2 weeks ago, the female a week ago. Got them from the same store and same tank, they are the same size. But the male just hates the female. He chases her off (not so bad), but then he has an all-out fight with her trying to bite her on the back and eye. She's getting quicker, that's good. No damage done yet, that's good. They are healthy, eating and active, coloration is great. All good things. The only thing I could think of was the size of the tank. Water peramiters are good, 0 ppm amonia, nitrite, nitrate, 7.2 ph and I have the pump bubbling on high for extra water movement. They have flat stones to rest on and planted lightly. But its just a little 2.5 gallon tank (fully cycled). A bigger tank is not an option right now. Could this be the problem? I think she's adorable, but he doesn't. Any ideas?