Fish thoughts
Rams - I'm very fond of these fish, they have interesting behavior & colors (I have some electric blue juveniles at this time, but would've gone with gold rams if local shops has anything beside "balloon" rams - which I consider to be a very sad fish, wild type rams are also stunning). As with most cichlids, begin with several juveniles & remove "rejected" fishes - sometimes rams will settle into a group, other times you'll end up with a single fish running the 60cm tank.
Angels - I think a 60cm tank is too small for adult angels (though breeders will often keep a breeding pair in this size of tank for spawning etc BUT if there is a "divorce" the rejected angel will often end up in a bad way: the most stable pair are formed from a group of several juveniles, breeders attempting a particular cross will condition males & females separately, then add female to the breeding tank followed by male a few days later, then remove both after spawning. I believe there are a few angelfish forums, TAFII is still active though I don't know how many breeders are still posting ...) This is a nice size tank for growing out baby angels, then move them onto your 120 cm tank (or return to lfs etc). Angels won't do well in a "river" tank set up, but they should be fine with most filters used in planted tanks.
If you're concerned about current, choose angels with "standard" fins rather than "veil" or "longfin"
Steve Rybicki breeds outstanding angels - location won't work for you I suspect, but look at his fish for an indication of well bred & properly grown out angels (look at the fins, any bent or damaged fins reflect poor water quality during grow-out).
If you raise baby angels with a group of tetras, the angels are less likely to see the tetras as prey ... I had a group of altums that were able to distinguish between the several rasboras they'd grown up with & any new additions to the rasbora school (which were hunted in the night).
Checkerboard cichlids - more likely to settle as a small harem in this size tank than other dwarf cichlids, I believe these are still mostly available as wild caught so you need to begin with a group of at least 5 - 6 juveniles (I've only kept them in a 90cm tank but others have success with 60cm tanks). Behavior seems to be somewhat locale dependent, I had a previous group that were awesome "schooling" fish, present group is very different in behavior but still very "kind" to conspecifics ... they seem bemused by the territoriality expressed by the much smaller juvenile rams (they just ignore or give way, depending).
They are seldom alone, but almost always in company with at least one other checkerboard, & more likely, a group.
They are rather "thoughtful" feeders so you need to choose tankmates carefully.
If you can find them, these might be an
interesting fish with either rams or checkerboards - with angels, I'd stick to more agile fish or a larger type of hatchet fish.
(awesome rock scape!!!)
