Coralife 20" lamp... higher wattage?

Recently, I did some reading to determine the answer to the same question. The length of the tube is what determines the wattage. For example, the 24" tube on my 25 gallon tank is 20w. If I go down to Home Depot and check out the fluorescents, I will find that the 24" tubes are indeed 20w. The 12" tubes are 8w. Therefore, if a higher wattage is what you're looking for, you will probably have to consider a new fixture. Now there a bunch of folks on this site that have way more experience than I and can provide more information. I have not begun to research the options for a different fixture; however, there are numerous posts that discuss the options, benefits, etc.

I just realized I answered your question from a fluorescent light perspective. Sorry.... better check the fixture. It probably says what the max wattage is and I believe you only have the one choice, unless you build your own, retrofit if possible or purchase a new fixture.

You have now a 28/32 watt CF (PC) lamp. The next size up is a 36 watt PC. Which is ~17" long. It should fit in your hood.

As to wether your ballast will drive it, I doubt it, coralife uses 28/32 watt ballasts, which will not drive a 36 watt bulb (it may light up, but wont be running at 36 watts, and will shorten both bulb and ballast life). You could purchase a larger ballast (workhorse 5 for instance) that will drive the larger bulb.