T5s are a great choice for nanos, however I would be a bit hesitant to get the 18" T5s because there is very little bulb choice. Personally, I would go nab a 15 or 20g tank instead which will be 24", and you would be able to get a better fixture with better bulb choices. I'm definitely not a fan of the Current USA brand...I would prefer Hagen over them, and that's sayin something!!
The 24w 24" T5HOs are also a bit more intense than the 20w 18" bulbs so that would be better as well.