Oh I forgot, if you get roach/rudd or similar cyprinids, don't place the tank at location where there is lots of noise and/ or cats, they freak out very easily and will bang into the glass.
I would recommed getting a chub ( hence my username) get to a nice size, look great, eat anything and lots of it and are very easy to care for.
If you have further questions, feel free to ask me
how about something like a single tench with a large school of stickleback for more movement. tench look stunning with there metallic green body and red eyes.