Okay, first of all I am a loyal follower of your website and you guys have helped me out a lot. I have a 120 US gal. tank. Unfortunately I am guilty of not being able to give every deserving fish I see a home. I currently have 2 5in Os, 1 3 in O, 2 5in JDs.,2 6in Parrots 2 2in Salvinia,1 3in jewel cichlid, 1 7in Pleco. I know way way overstocked. Could my tank handle the 2 0s 2 JDs and the 2 Parrots if I get rid of everyone else? I have 2 Emporer 400s that filter 400 gal ph each(both are full of bio balls) and I also have a 1140 power head on a sponge filter(it is 300 gal ph).

2 oscars and a plec would work best.

I agree, 2 o's and a plec, or a JD.

and you could always add another tank! LOL

Ammonia problems??? you don't mention ammonia? whats the problem with it? your filters should be able to cope with ammonia produced by your fish, you should be suffering nitrate problems if anything. you do need to lower your fish stock to a more manageable amount. i won't suggest what fish to keep but a tank your size should cope well with 2 oscars and 1 or 2 medium sized mates. any more and your going to have to put a lot more work into maintaining the water.

yes... i agree with marcus.
or are you afraid of potential ammonia problem???? with your current stock,
ammonia would not be the only issue that will comes along...

I reckon you will be ok with a couple of o's and 1 or 2 smaller tankmates and a plec, but be prepared for large weekly water changes and plenty of filtration