I use the brightest white light I can find in standard compact fluorescents.
I've seen some compact T-2 around, just not the right wattage for me.
Since my tanks are all planted, I aim at 6,700K with the highes
lux or
lumens possible. Unfortunately some manufacturers provide less than minimal information. High end Ks lamps, say 18,000K or 20,000K might be needed for deep tanks (e.g. over 26" H).
A full spectrum bright white light might go from around 5,000K to 6,500K; a super bright white light (not available locally) might work better.
I am using cheap clip-base lamp assemblies to lit the rear end of some tanks. Those standard clip-base goose neck lamps have a fairly good reflector. My plants are grateful for that. I'm trying several CFs models (from 11W to 27W).
I purchased and still using until upgrading the lamp, several sealed garden lamp assemblies from a hardware store rated at 3,000 and 3,300K. This light is really yellowish looking but kept my Black Amazon Swords OK for months. I am installing those incandescent-socket ready, bilt-in ballast, 21 to 27W CFs in those units, so I'm only using the case (keeping the 13W transformer and 2 clip socket as spare parts) added a socket and tested for temperature problems: none so far, and these are lit 12 hours per day.
Pepe
Santo Domingo