Diversity and they will eat the snail population and keep the parasite that snails can carry down to a minimum. Plus they eat real good. The RES that is
convinced me!! I want me somes red eared sunfish!!
You want them because of their gentle and nurturing disposition to all the other fish in the pond. Read all about it here. RES love of new puppies and children
My pond was a mess with parasites and snails until I put my RES in there. Man they cleaned all that right up in 2 years. Ya got to have them just for the maintenance they do. I catch most of mine on worms and crappie minnows. Maybe a small rooster tail.