Oh no, you can pretty much just feed mash, if it has a good balance of grains to pulses (about 2 parts grains to 1 part pulses) and they make about minimum 50% of mash with veg the other 50%, plus some good nuts for good oils. It is just generally they don't need to eat all the time. Three straight meals is more than enough, even if there is no seed in the cage at all. If you are worried about giving just 2 meals you could give 3 meals and give about 1 teaspoon of seed between the meals, so making it 2 teaspoons in total. Always look at the poop - if they are of a good volume then he has got enough food in him, if at times they turn into plain water then you could top up his seed bowl by another teaspoon for example.
