Question on ovestocking a fish tank....?

[rolf]

I own a 30 gallon(approx 80 ltrs) fish tank. In this tank i have ATLEAST 11 Goldfish(Shubunkis,Orandas,Pearlscales,Bubble-Eye,Black Moor,Calico & Lion-Heads), 3 Iridescent Sharks, 3 Bala Sharks, 2 Red-Tailed Sharks, 2 Serpae & 5 Widow Tetras, 3 Plecos, 1 Male Pearscale Gourami, 4 Giant Danios, 1 Zebra Danio, 2 Boseman's Rainbow Fish, 2 Butterfly Mirror Carps, 1 Female Guppy, 2 Female Mollies & 2 Apple Snalis.... On top of this I have dark gravel, lots of artificial plants, 1 Ceramic Castle & a bogwood as decorations.. I have a Powerhead & a Sponge Filter plus an Air Stone for EXTRA oxygen & a heater....I feed them CP Classic pellets,Tetrasun Real Gold Daphnia Flakes, Freeze Dried Tubifex Worms,TetraBits Complete Granules & ocassionaly live mosquitoe larvae.....I change 10-20 ltrs of water every Sunday....My question is how in the hell are my fish are allright(lol)???? On normal circumstances my fish would've EASILY died bcoz of high amount of ammonia OR overstocking the tank as the "EXPERTS" say but non of my fish have died since more than a year....How do u think my fish have actually lasted this long???? Anybody can answer but I want the "EXPERTS" to answer this question....10 pts to the BA!!!!