It sounds like they are increadibly over crowded. Most "Lake Fish" need a 125 gallon tank. I want to set up a tank for a N. Pike, you have to have at least a 75 gallon tank and they out grow that in one year. My friend managed the aquarium section of a large pet store, he told me I could have any lake fish in less than a 75 gallon tank. Even the shiners sound over crowded. How big are they now? Your best bet is get bigger tanks.