Culling fish from a pond is one of the best things you can do to maintain a healthy population. You said you were culling fish but still having issues with some fish be slender in size. I think you need to cull some more and when you think have have culled enough Remove Some More...you will be surprised at how many pounds a persons needs to remove to keep the balance in check. This only applies if you have a pond that is capable of producing fish like the number you say you have...cull harder,it will pay off in the long run.