What else can I do?

[Enigma]

Just be aware that Scarlet Skunk Cleaner Shrimp do not tolerate H202 exposure well: they are one of a few "intolerants." You didn't specify what kind of cleaner shrimp you have.

I routinely use 3% for 10 minute dips (1:10 H202 to tankwater), and I've had very good success with it. For dipping corals I would stick with the lower concentration. If you'll be dipping your rocks, then I would use the 35% as it will stretch farther.