What lights to buy?


I'm about to upgrade the lighting on my 29 gal. tank and would appreciate some 
advice. Looking through my saved messages on lighting from the past several 
months has given me a good start, but I have this feeling that I probably have 
just enough information to be dangerous!!

The tank size means I'm stuck with 24" bulbs, which limits choices somewhat. I 
have found Phillips F20 T12 bulbs with a 5000K rating for $5.50, which sounds 
good after the $19 - 25 prices of "aquarium" bulbs. I am under the impression 
that a 5000K fluorescent bulb is a 5000K fluorescent bulb; is that correct? (
at least to a first approximation.) 

Now for the ballast. I've found an electronic ballast which will run 2 40w 
tubes. The guy said I could put the shorter, 20w tubes on it with no problem. 
Is he right? (You notice I trust the APD posters more than the salesman!) Is 
it likely to work to run two tubes? or do I need to find one specifically for 
my bulbs? What other questions should I ask? This ballast is $28.

I also need endcaps and starters but I'm less worried about them as they seem 
to be easier to match up once I have the tubes and ballast. Or are there 
components I've forgotten?

Many thanks in advance for your help.

Christine, in HOT Palo Alto, good day for the pool!