Finnex. I have both fixtures, and I don't think the Coralife would be great on a 29. It seems barely adequate on my 20H, and has already shot a pair of bulbs in about 6 months. Plus, Coralife is the only producer of 30" T5NO bulbs, so you will have no other option for replacements. Meanwhile, plants are going nuts under the Finnex in a 38-gal.