So I have an Exo Terra dual fluorescent canopy that fits 30" bulbs which seem to be near impossible to find. I have the 30" reptiglo bulb already but the fixture won't work without a second bulb.
As I said, it seems to be impossible to find 30" bulbs of any sort.
An 18000k light sounds pretty intense (I haven't seen one but read they're used in saltwater setups which tend to be very bright). It may be worth a try but I'd definitely provide lots of shade areas. It may be too intense at the distances needed for a T8 UVB light anyway. It is probably a better idea to scrap the fixture if you can and go with a more common size or even better to swap up to a T5 fixture and bulb which will be nice and bright on it's own.