It's really up to you...
If you want to completely get rid of them bait them with vegetables. Don't add fish, especially if you do not want the fish.
If you just want to lower the population cut back on feeding.
If you like them, keep them. I have never seen them to any harm to plants. They should only be eating dead or decaying plant matter anyways.
I personally liked them but had too many. I tried a combination of the first two and it worked well. My cichlids also helped