[Nathans_Dad]

I have a 29 gallon freshwater setup.

I would agree about the food. It is very easy to overfeed fish. If you do the food will just sit on the bottom and foul the water, which is what it sounds like is happening. Feed only enough food so that the fish eat it all within a minute or two. Remember that fish have to scrounge for food in the wild so it is ok for them to not be stuffed with food all the time.

A rule of thumb is one inch of fish per gallon of water. So a 16 gallon tank should have no more than 16 inches of fish. If you have 10 fish and one of them is 3 inches long, I would bet you are bumping up against the max load for your tank.

Water changes should be about 20% or so of the total volume every week. Sometimes I will do a 30% change but not more than that or you risk stressing the fish.

Always overfilter your tank. I have a 29 gallon setup but the filter I have is rated for a 50 gallon tank. This will allow you to slightly overstock the tank while not overloading your filter.

I would advise cutting the food down, do several 20% water changes over the course of a week or so and maybe pick a few fish to get rid of. If you don't have any catfish in there, I would consider swapping out for a couple catfish, they will help eat any extra food that makes it to the gravel.

Good luck!