Brown growth

I have a nearly constant brownish growth on my sandbed and one side of my tank.  The tank gets some sun on that side during the day, which I understand is not optimal, but at this point moving a 55 gallon full tank is not really an option.  My understanding is that you can get that kind of growth also if there is not enough water flow in the tank, and I am running 2 hydor nano 240 gph powerheads as they were in my 29 gallon before I upgraded.  My question is, would upgrading to something with more flow help with this issue?  Or is it more likely that I need to convince my wife to cover that window better to not let as much light through?
I don't have a good camera or I would post some pictures, but if it helps I can take a couple lower quality ones with my Iphone of the brown patches.  Basically I suck that portion of the sand out weekly with my water changes which reduces how brown the area is greatly, but it then over the week increases how big and brown it is.
Thanks,
Charlie

 

This tank is 2 months old at this point, but everything in it came from my 29 gallon which was about 5 months old. So it is still relatively new as far as tanks go.

 

Yeah I have snails and crabs over there a lot helping out, but I end up siphoning a bunch out every Friday when I do my water change. Is there anyone in the Des Moines area that sells the correct type of cucumber? I ordered one from Florida a couple weeks ago for that exact reason but it didn't make the trip. I understand there are some that are filter feeders, and some that actually burrow in the sand bed eating detritus.