I'm a little stuck..

[Kenidi]

I am pretty new to the world of fish, but it only took me a few days to realize I was hooked. I bought my first tank (a 10 gal) about 4 months ago, and I (stupidly) didn't do any research on cycling or compatibility or needed equipment. I bought everything (tank, filter, gravel, decor fish) the same day, and put it all in within 10 minutes of each other. I had 1 Tiger Oscar, 1 Dragon fish, 1 peacock eel, 1 bristlenose pleco, and a fish that petsmart told me was a turquoise cichlid, but judging by the pics on google, I don't think that's what it is. Amazingly, nothing has died, or even seemed sick.

About a month later I found out about cycling and realize what a lucky break I had. I learned all about water quality and such, and I got a free 55 gal glass tank off of craigslist, and it is now fully cycled, but I haven't transferred my fish yet. I am kind of stuck with that. Not transferring really, but I am trying to make sure I do this the right way this time. I want this to be an amazing, well-stocked tank, but I am not really sure if I can put any other fish in the tank. I keep thinking that somehow my random combination of fish I already have, has somehow formed a gang that will be completely incompatible with any other fish. None of my fish have ever been aggressive at all, so maybe my fear is unfounded, but every time I look into new fish, I remember those horrible little red tags at petsmart denoting how evil nearly all of my fish are.

I love colorful fish, and *kick a** fish (like a stingray I would like to get if it's compatible), but I don't want any of my fish to get hurt or worse because of my ignorance on the subject. Also some of the fish I have been looking into are more costly, like a flower horn. I just really don't know what to do. I don't know anyone else interested in this wonderful hobby, and it seems every other site I try to do research on, says something completely different. If you can offer any advise at all, it would be much appreciated!

[ZeroSystem]

Cichlids will get more aggressive once they reach maturity. You have little guys now but once they've grown up they will become very protective of their territory. In my opinion a 55 isn't big enough for an Oscar let alone and Oscar and other fish as well.