Had you a few years of experience under your belt keeping nano aquariums AND a bigger light than that I might say it'd be OK... But, given your current cirucumstances and lack of experience keeping water chemistry stable (a clam really puts a load on the aquarium in terms of alkalinity and calcium demand) I would not reccomend it.
*snicker*
I suppose I should read the whole post instead of quickly skimming it![]()
Then again my answer would still be the same. If the blogger has a lot of experience with nano tanks and chemistry dosing, he might be able to do it longterm, but I wouldn't do it with ONE 18watt PC lamp... MAYBE 2, but then again you only get away with it cause a 2.5g is so shallow...