my P.senegalus lives in a 10 gallon tank and one is getting bigger and one is staying the same size or little bit smaller why????? 
cuban jey said:probably one is quicker at hunting than the other try handfeeding the lil guy
Gooda said:a little size differance isn't a big deal. But if you are worried about the little one eating you could feed them, and when the more agressive one is full, you could put in some ghost shrimp, or somthing east to catch for the other one to eat as he wants. If he dosn't seem to be hungry, it might just be the individual. My smaller Birchirs go through phases all the time where they will eat really big and then not touch any food far a day or two, but they always snap out of it. And they always endup growing rediculously fast...