If everything gets covered by algae only 2 days after you've cleaned everything off, a CuC wouldn't be enough to keep that kind of growth in check. What equipment do you have in the tank? What kind of sand bed? I would start with getting some Microbe Lift Special Blend and begin using it per the instructions on the package. Take the rocks out of the tank and scrub them in a pail of water and keep doing it. Eventually you'll it'll slow down it's pace and when that happens you can worry about a CuC for keeping up with the slower growth. The reason I asked about equipment is that I try to clean mine every six months, when I don't it gets clogged up with detritus and I start growing more algae. I recently had a small outbreak and upon removing my rocks to reach my pumps so I could clean them I found a dead stinky snail. Cleaned it all up and have been algae free for a few weeks. Getting worried that my CuC will starve Anyway, sometimes it pays to just break some things down to clean them and look around for a hidden problem like a dead snail.