I've had a rather large amount of experience with cyano. This stuff SUX.
Chemiclean, temp sol'n and the bottle says so. Not only that it deprives the water of O2 so you have to really agitate (air stone) the water for a day or two while dosing so you dont literally drown you fish.
Hermit crabs have never touched the stuff, neither have the snails, any shrimp, etc etc. Nothing really eats this stuff.
BEST Solution I've found:
Your phosphate levels are probably through the roof. City water is horrible for that. To fix: Use RO/DI water AND/OR use phosban phosphate remover. This will get those levels down. Cyano LOVES phosphate for some reason and will grow like a weed if those levels are even slightly higher than normal.
Once your levels are to 0 or better
Use the scrap and suction method to get rid of the remaining cyano. Once the majority of it is gone, and the phosphate levels are down, you should notice the remainder of it dissapate into the skimmer.
Cheers