Just buy an automatic feeder, you can set the amount to come out. Petsmart has some pretty good ones, they are 20-30$. I have one I use to feed in the morning so that when I am ready to go I can make sure all the food is gone. When I leave on vacation or for work I just set it to feed two times a day and knock down the amount a little bit so they will not be over eating and there will not be tons of food floating around.
I also got my lights on a timer so they still come on and go off, if I am gone for a real long time, like more than a week I will have someone go and check the feeder and fill it up. Its a piece of cake, that way you dont have to worry about someone over feeding them. Set up the autofeeder a few days before you leave so you can adjust the amount to the right level and the fish will get used to it. Mine now know the sound it makes and rush to the top the minute it starts turning just waiting for the pellets to hit the water haha.
I dont understand why you would rather starve them than possibly feed a little less but at least know they get a little something each day. Do a WC before you leave and when you get back and everyone will be super happy.
Mine always seem to be a little extra bright and colorful right when I get back. I think its because my apartment is real quite and there is nothing there to scare them or startle them when no one is home for days on end.