The thing you have to remember is that the force of the water coming into your 29 will disrupt your sand and such and then the return pump will spit cloudy water back into your tank.
You need some kind of divider. Currently I use a 20 gal
glass tank with a small rubbermaid type container acting as a barrier/wall. It is a tight fit but it stays in place and works great as a bubble trap. My drain line dumps right by my skimmer and the water then flows underneath my makeshift wall to my return pump.
If your skimmer and filter are HOB
models, then you should have room for a fuge in there but you still need to keep the drain line and return pump separte from any sand or macros. Baffles are used as bubble traps and with the drain, filter and skimmer dumping water into the 29 gal
, bubbles will be created.
You could always go to HD
and buy acrylic sheets to silicone into the tank.