Hi all, I have been pondering for some days already how I should best combine my fish (primarily the cichlids) when I'm getting my new tank. I currently have ~65 gal (48x20x20) and am now getting a corner tank of about ~100 UK gal (too lazy to try to convert the dimensions now, it's 24 high I think).

I have way too many fish in the old tank, and although they're healthy and the water is ok as well there is some trouble starting now. The fish are:
1 adult Oscar, very well mannered
1 adult Firemouth, very small but getting him-/herself into trouble
1 male Nicaraguense, should be adult size now
1 male Green Terror (well Goldsaum), still small but the reason for my worries
other fish are a red-finned shark (doing surprisingly well in there) and two catfish, think female Bristlenose, neither big

I had been dreaming of a real long tank but since there is no room, these two gotta do. So which should I put in with which in which tank?
I had been thinking the Oscar should go into the bigger one due to his size, but not sure about the rest. Strangely, the both that get along best currently are the Oscar and the Terror, no trouble ever. I'm worrying though that once the Terror gains in size (think not even 5" now but ruling next to the Oscar), he might turn against my big baby, and I'd really hate that.
I've read that Firemouths are recommended with Terrors often, but doesn't work at all for me. During the past 2 days the FM had to take quite a bit from the terror and starts looking shredded.
The Terror and the Nic don't get along neither but no harm yet due to the size difference. The Nic neither does well with the FM but can't do much harm with his small mouth. (The FM had been picking on both of them when they were small.)
The Oscar doesn't do harm to any fish, even tolerated an Angelfish temporarily although he wasn't too fond of it. He seems to have a liking for the Terror though and even supports him when the others get defensive towards the Terror.
So any ideas and experiences on how best to spread them between the two tanks? I don't really want to end up with only one cichlid in one tank, but if all else fails, I could always get another i guess

Blimey, you've got a real mixed grill. Personally, I would put the Oscar, fire mouth and green terror together. Put the rest of the fish and the other tank. This way, you are keeping all the fish that could be aggressive together and away from fish that may not defend himself as well. Just remember that green terrors can be very aggressive so watch out when it gets bigger.

True, that sounds like a plan.
With the combinations I'd had in mind yet, it would have left me with either a lonely Green Terror or a lonely Firemouth. The Firemouth is by far the weakest cichlid in the tank, but think in a corner tank it should be well possible to create some hiding places for it where the Green Terror can't get. (Well he's the size of the Firemouth but double as fat and will have outgrown it soon anyway.) And if the GT turns nasty towards the Oscar, I can still swap him with the Nic. I just gotta refrain from adding any fish to the Nic tank that might not be compatible with the GT then later :/
Not worried about the non-cichlids at all, they are completely ignored most of the time and can hide fast.

Sorry about rambling on on that, really keeps bothering me, I hate to have fights.
Thanks for the input!

All individual fish are different but generally green terrors are mean. I had to get rid of one that was battering an oscar twice its size. Firemouths give it the large one but rarely damage another fish and when fronted back they back down. The Nicaraguense probably wont be any hassle.

I think you just have to try a combination and see how it works out but i suspect you might end up with the terror on its own and the others together. Let us know how things go

Now I kind of feel as stupid as before, hehehe.
Think I will either do as Penn suggested, with the option to swap the green terror with the nic later, or keep the green terror alone from the start. He's certainly the one that can do the most damage. The meanest one is the firemouth, just can't do a thing against the others - almost killed my nic a year ago when I added him, had to be taken out till the nic grew bigger. The nic and the green terror are even at the moment but need to be separated soon. And the Oscar won't start any trouble ever, he's even scared of wiggling insects on the surface.

It will take some time still because I need to do the flooring still where I want to put the new tank, and I'm not really talented Thanks again!