Fish can be rather stupid when it comes to feeding. They will often times eat as long as food is available and I have even heard of fish eating to death. Rule of thumb is....feed a small pinch at a time, if none of it hits the bottom, then add another small pinch. Once the fish are no longer eating it all before some hits to bottom, then that should be enough. If you have inverts, then making sure some gets to the bottom is good to give them a variety in their diet. Just my own experience, and it has worked for me.