has your siphon got a bigger tube on one end?
......mine has the tube which leads to a bigger tube that you put into the gravel.....I clean out the tubing every now and then cos that gets sludged up and the flow slows.
Your gravel may be clean which is why the siphon isn't picking much up....but yes imo do need to get any uneaten food and fishy poop out of the tank
sue
