yeah, or just starve them.
When i first got my checkerboards they refused to eat colourbits in my tank, but ate mainly them at Ron's place.
I couldn't be bothered with their antics so i went to new plymouth for a week, fed only the bottom dwellers and when i came back the discus ate what I gave them.
I like feeding discus tucker cause i can see their fat little tummies, and the clean up crew do a great job with the extra bits.