I also work at PetSmart and we use the small Koi for snail control. They do a better job than anything else and pick off the snails without eating the other fish. We donít stock enough clown loaches to do the job. I wouldnít use feeders in those tanks though.
If you donít like the idea of fantail goldfish and Koi with the tropicals you should know that at PetSmart the fancy goldfish and Koi are on the same system so they already share the same water. The only ones that have their own systems on the wall of tanks are the feeders.