At risk of being labeled “tang police”, if you’re looking for a tang for your 30g, IMO that’s too small of a tank. Tangs need lots of room to swim.
I’d love to have one, but I only have a 32g biocube right now.
Depending on how much GHA you have, a sea hare works great for getting rid of it. Just make sure to supplement with seaweed or get rid of it when the GHA is gone.