Phosban reactor vs. GFO

I have never had a crab eat any algae with the exception of red "Cotton Candy" algae and then only snails hand caught in Baja Mexico worked.
Not all snails are good for hair algae either, turbos seem to be the best for me along with astreas but the can't right themselves and die an maybe Margarita snails. I keep lots of others but they stay mainly in the sandbed eating detritus not on the glass or rockwork.