I'm not familiar with that brand, but I assume it's some sort of Phosphate remover? I've used red slime away with great luck before, the tank looked ugly for a few days (worse than with just red slime, air bubbles bonded to everything in the tank), but after that it cleared up the slime.
I did recently use phosban, and it really worked to cut way back on hair algae, but I think it killed the clam I had in the tank. I read that small granule phosphate remover (as opposed to bulkier Ferric Oxide) has a tendency to be dusty and that the dust is harmful to clams. I was very bummed losing my clam, and unfortunately, I'm now 3 for 3 on clams, so I will not be getting anymore since they are all wild gathered.