For $20 save the tank for something else!
Mine lived in a 20L for several months, and only jumped out once. LOL
They get more shipments of tanks every week. I they are out of 40s, just ask them what day they get their shipment, and hit it in the afternoon that day.
And no, I would not use a pair of 10k T5s. I'd run 100% actinic bulbs if you can. Heck, a pair of T8 bulbs would be plenty. You do NOT want too much light, and don't want it too white.