What to do with new 25 gallon cube?

Given the footprint I'd just do some shellies...a colony of multis would be nice.

plants

Best tankmates would be livebearers (platies, endlers, guppies) or maybe some smaller rainbow species. Really isn't anything small enough from Lake Tang that would fit...

Nothing Multi's are not a community type of fish so i would stick to a species setup if you want to add different species than do a community setup, As for Multi's will do a nice job adding young fish to every niche of that tank..

I agree with Pitt, if your going Tang, small shell dweller species tank is all you can successfully keep. I have a 125g with 7 adult Multi's occupying 1/3 of the tank, and 10 Juvie BCWP's in the other 2/3's of the tank. The 7 multi's and their fry are filling up their area quickly. I had thought of adding a third Tang species (big tank, right) but glad I waited. I do have furcata's as dithers, they swim 99% of the time at the top 1/3 of the tank, at feeding time, when they venture into the Multi's shell bed, they get attacked at all angles. Needless to say, they don't go into the Multi area often.

I would also like to throw out going planted. Makes for a beautiful cube.