6.6 gallon planted M.praecox
It's just a 6.6 gallon - the common and popular bookshelf version. I'm looking to upgrade to a 20 gallon for this particular outfit as soon as I have the funds.
I have four tanks, each containing a different species of rainbowfish - the other tanks are much more utilitarian and purposed for breeding. Every morning for several hours, and sometimes again in the evening, the rainbows flash and put on an incredible display. If you've never seen it they are truly swimming sparkling gems. When not exhibiting this spawning behavior they usually seek the comfort of the heavy planted tank. Sometimes you can't even tell there are fish in there!
I think the safety they feel in the plants contributes toward more of the beautiful spawning displays. If you ask me, rainbows cannot be beat. I think M.kamaka or M.boesemani (I like the Ayintjo variety the best...) would look great in a 45...