JEBO makes some nice 9-13watt clip on cfl lamps, not sure where to get them though if you live in the states. e-bay has them but sometimes a little over priced on the shipping.
i was kicking around the idea of some drop lights used for working on cars. their cfl 9or 13watts also and you can find them pretty cheap but i found the $20 home depot lamp 27watt might be a little to much for your setup

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i think around 10 watts would be ok. when thier small tanks the whole wpg rule (IMHO) goes bye bye.
i also think the no filter idea is ok i plan to do the same on my 4 gal.
Jeremy