Six

I'd definitely look at the congos first in regard to eating tankmates. Especially if you add a new fish to their tank- they're going to think you're feeding them when you put the new fish in. They may be aggressive in that situation and cause damage or stress to the new fish. Stressed fish can equal dead fish pretty easily. Or the new fish may not have been the best from the store. If my fish die in a week, I get a little wary of the store's batch and maybe go back to look if they also had some die off.
Were the congos introduced after the neons? I agree, if the neons were introduced while the congos were in the tank they'd be a good lunch for the congos- or would get chased and stressed quite a bit.
Also, if a fish is dead in the tank, the other fish will definitely eat them no matter what species they are. That's just fish. The r'bow is probably eating the remains first since he's the scavenger of the tank.

I;d choose between having a semi-aggressive community tank (congos, r'bow shark) OR peaceful community (neons, small rasbora, etc) and add fish that fit into those.

GL!

Jeanine

Here is a picture of my tank. It is a 55 gallon. I recently did some major pruning because there was no room for the fish to swim. Plants were literally growing out of the water.
I would like to go with smaller tetras. The Congos were a disappointment because I got them when they were very small, and thought I would get about half male. As it ended up I only got 1 male out of the 6. He's very beautiful. The recluse rainbow shark still rules the bottom of the tank, and I may have to put up with him until spring.
Thank you all for your advice.

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Six

heck, id be happy with that many females- i like to breed my fishes though... hehe. on the good side, that male is probably very happy!