What is "overfeeding"???

I am sure others will explain it better,but if you tank is cloudy and looks dirty,you have ammonia,nitrite,and high nitrate readings,even though the tank was cycled,and you do regular water changes,if you can see food sitting on the bottom of the tank,you are probably overfeeding.
I have never understood the rules of feeding either.I just feed my fish a small amount once a day.They have all grown,not died,and seem healthy,so I figure they are eating enough.My water parameters are also fine.

Overfeeding usually entails feeding foods more than necessary to the point the fish simply start ignoring the leftovers that get trapped into corners where they won't likely see the foods or just cannot retrieve them easily. The food simply rots in the process thus your ammonia and nitrite start elevating dangerously. Your tank would even reek badly of ammonia. Food leftovers must be siphoned out of the tank immediately if the fish start ignoring them. When you do this, it does involve water changes but water changes really will not hurt your fish. In fact, your fish while well fed, will also remain happy with very clean water.

Feed your fish sparingly. This is up to common sense. You need to make sure you are feeding your fish adequately but not to the point they look extremely bloated already from the foods. Feeding them small amounts of food multiple times a day is better than feeding them a few large meals where the risk of bloat or constipation and uneaten foods rotting around is much higher.

Young fish tend to require more feedings than adults so you will notice rearing tanks tend to get more frequent water changes than tanks with only adults. In my case, I feed my young goldfish 3-4 times a day with homemade gel foods, bloodworms, commercial foods, etc. As my tanks are barebottom, uneaten food usually is not an issue at all and water changes are done 3-4 times a week to as much as 80%.

I'm a chronic overfeeder. I'm very forgetful about feeding my fish (they don't whine like the wife, kid or dog), so when I remember I generally feed to much.

There are no absolute rules that work for all species of how much food to give to a fish. It depends upon the species of fish and what type of food you are giving them. There is also the personality of the fish to take into account.

For fish that only eat from the surface or water column, you really need to try not to feed them more than they can eat before it hits the bottom. These fish often require many feedings per day.

For fish that eat off the the bottom sometimes more time can be given. One feeding might take them up an hour to eat.

It takes a little time and effort to learn what you should feed. To little and you and cause illness and disease. Too much and it can ruin the water quality and kill your fish. So the only way that I have discovered how is by trial and error. If the fish are asking for more right after you feed them it wasn't enough. If the food starts to cloud up the water you fed them too much. When finish eating and lean back, let out their belts, unzip their pants, burp, and then pat their bellies you know it is just right.

I give my fish about 30 seconds to a minute to eat. They are crazy eaters and I think they would eat all day if I let them. Even at these short feedings I still have some chubby fish. I'm trying to find a happy medium as well on feeding. Pretty much it's better to underfeed than over feed.

I feed mine a little at a time. if they finish right away a sprinkle a couple more flakes. Once a see ignored leftovers I net them out so they dont sit on the bottom .

I've never seen ignored food in my tank

depends on the fish really. for my guppies, i really only have to take a good pinch, crush it up and they are set for the day. the goldfish dont eat as much as you'd think either. i have to sink there food. i do it pinch at a time to make they are eating it all.

Fish will eat all day long if they are allowed to. Mother Nature does not feed the fish 1 or 2 times a day. If a fish is lucky to find something to eat, it does. Look at your fish, do they appear to be 'thin' or 'fat'? I feed my fish 3-4 times a day, with that said I feed very little at one time. I skip feeding one day a week. If your tank looks like a 'snow globe' when you are feeding then you are doing something wrong.