Prob. cichlids and loaches isn't too bad if you kept the tank's pH around 7.5. It's a little, but not too much on the low side for the cichlids, and it's at the high point for loaches. Of course, I'm a purist when it comes to ACs, and like biotopes. Up to you....
The rainbowfish, on the other hand, would go fantastically with the loaches; esp. since they're from very similar parts of the world: Clown Loaches from Indonesia, Most Rainbows from Papua New Guinea and other islands, down to Australia. Sigh.
I knew you wouldn't go for the rainbows. That's ok. Your prerogative!! I don't want to hoist my fish taste on you!
Well, last time I wanted ppl to get interested in a bunch of fish they seemed less intererested in, I had to buy some and take pictures (dwarf puffers). Perhaps I'll have to buy some Praecox Rainbows and post the pics. Then, maybe, you guys'll get interested! I'm mad about the quality (low) of the rainbowfish pix on the net.
BTW, rainbowfish are the perfect size (3-4 inches) for a 55, and are a little cheaper than ACs.
********Just out of interest... how come ppl here aren't interested in rainbowfish?? I've only seen 1 member with a boesmani, and he (the fish) died...********