I have one on my 75.
I'd recommend against putting this in a 29. It is 8 inches wide, about 7 inches tall, and about 2 inches deep. That's alot of real-estate in a tank that small.
Aside from the size issues, I have to say I'm not overly happy with mine anyway. You have to really keep an eye on your water levels in order for it to keep the surface water clean. Too high and it doesn't skim the surface water properly. Too low and you interrupt the water flow into the skimmer which screws up the skimming process.
It's also attaches in a pretty annoying fashion. There are two screws located on the front of the box that you turn until they make contact with the powerhead. Then you just tighten them until you get enough pressure to hold it in place. While it does stay in place, it isn't a very precise method of getting it there, and I find myself having to make multiple attempts at getting it attached at the height I want.
Don't get me wrong, I love the skimmer and couldn't be happier. But the surface attachment leaves alot to be desired.