Thats not exactly the most nice way to do it. Another way you could get them more comfy from eating from the top is put some floating plants/driftwood on the surface....fish are scared to come to the surface to feed cuz it makes them feel 'vulurable'...thus some cover will make them feel more comfy. Also try dimmin the lights...like turn the lights on the tank off but leave another light on that still shines some light on the tank....that way they will get more used to eating with out fear. OR you could get some cichlids that already eat from the surface....thats how my pikes learned...

...from my other fish eatin from the surface. But starving them is a pretty sure fire way....as evil as it sounds....