Help!! Green Fly breeding in Tank

[cjdevesa]

For the past year and a half I have been fighting with a small green fly that likes to breed in my tank. Its not harmful I think, it must eat fish detritus. Anyway there are 3 forms in its life cycle that I can identify. Fly stage, must be an eggs stage, worm stage and the larval stage that swims to the surface and pupates into the fly.

I have removed all the fish put them in the garage, taken out my filter media boiled it and then bleached the entire tank letting it run through all of the filters for 4 days and up to a week and still they come back. I've done this 3 times.
Currently I'm trying a surface hagen surface skimmer attachement to a magnum filter with micron cartridge, but this only seems to be keeping the population down not eliminating it. This has been extremely frustrating.
I've also tried potasium permangenate, formalin and aqua prazzi. My next plan is to put the fish outside in a makeshift pond for a few months and bleach the entire tank again, this time for longer.
I've also raised the water level to the glass top hoping to drown them, to no avail.

Any thoughts or suggestions, something else that might kill the fly.
Is it possible that they are using the fish as a host at some point?

Tank is a 90gallon with 2 rena XP2s'

[Cincy Ranchu]

I have seen something similiar develop when short people feed my fish and the flakes and pellets miss the top of the tank and incubate on the plastic ledge on the top of the tank. Since the short person is my wife or grandkids, I get a pass and blame it on the ripe bananas on the kitchen counter upstairs.

My advice is to look for where the food is accumulating...