15gal setup recommendations

["dilvish" <dilvish at pacbell_net>]

About a year and a half ago, when we knew absolutely nothing about raising
either fish or submerged plants, we purchased a 15gal Eclipse, recommended
by a lfs. In terms of plants, this was a complete disaster. The fish
survived okay, but just about everything else that didn't swim never lasted
more than a few days.

Now, since our 6 month old 50gal is doing so well, I'd like to start again
with this 15gal.  I'm assuming that our problems were from the bio-wheel,
which made the water way too oxygenated and removed all traces of CO2 (not
that we knew any of this then). I believe the lights weren't sufficient
either. (and fish load.. I think we did just about everything wrong)

What would you guys recommend in terms of filters, etc. for a small tank? (I
have a couple of yeast/sugar CO2 cannisters that deliver the CO2 via a tube
& ladder mounted inside the tank.)  Are there any distinct differences in
the chemistry or cycling of a small tank as opposed to a large one?  Thanks
in advance.

Dennis