Yes it does. But its a little like getting rid of cockroaches in your kitchen by spraying DDT over the entire state. Its an antibiotic - Erythromycin - and is not at all specific to cyano - potentially killing the good with the bad. Our tanks don't work without bacteria.
While I don't disagree with the sentiment that this should be a last resort type of treatment, the reasoning is a little myth-based. While there may be exceptions I'm not aware of or products may have been diffent in the distant past, these red slime treatments all seem to be clones of Boyd's Chemi Clean, which is an oxidizer (as in Lugol's solution or household Hydrogen Peroxide) rather than an antibiotic like Erythromycin. Any products that are the same form (white powder in a little jar) and carry the same instruction to discontinue skimming during treatment are most likely clones of the same thing.
If you choose to try one of these treatments - read and follow the directions!!
The only negative side effects I've personally heard about from using one of these oxidizers were from someone who didn't read the instructions all the way through. In their case their pods and a few of their clean up crew inverts got zapped...nothing more.
Having said all that, I'll repeat that this should be a last resort. Red slime can get completely out of hand to the point it literally forms a blanket over all your rocks and corals. If your bloom is not this bad, then siphoning would be my first tool of choice against cyano, but there is a point where it can be bad enough that you really can't get enough of it in the amount of water you'll be able to remove practically. Using a product like Chemi Clean in this scenario can put a "reset" on the cyano and give you a chance to eliminate its roots. I would not advocate the ongoing use of a treatment like this.
-Matt
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