Newbie: small African tank

Hi all,

I have a small (36"x15"x12") tank not doing anything at the moment -
and it's long been a dream to have a tank of colourful rift valley
fish.

I've done some reading-up, but would appreciate any pearls of wisdom
about stocking this tank...

- is it worth it; is this tank just too small?
- If I can do it, am I limited to small Tanganyikan fish? Obviously,
colourful things like Labidochromis caeruleus is on my wish list - but
I realise this might be out due to size and aggression.
- What sort of density should I be looking at to start with? I'm happy
to invest big in filters if slight overstocking would help with
aggression.

Thanks for any and all help!

Toby