Joel, my NOs are 30 inch, that's what I liked. HOs are 24inch. Turns out I was wrong, I am using the HO but with just 1 bulb instead of 2, maybe that's why I didn't remember or notice so much. I recall shopping for bulbs, 30 inch is unusual
I haven't set it up and used it yet, but awhile back I picked up an "open box" Odyssea 30" (24" tubes) 6500K T5HO from eBay for $26 shipped...well actually $40 along with a box of 4 replacement lamps.. (Shhhh! don't tell the missus). I plan to use it on my 29g.I was hoping to use what I have, so maybe the 24" HOs.