"Ich" is an invert, and to kill it....you put all inverts in danger. I would NEVER EVER put it in my reef......this is a cut and paste from their website ............
Considerations for use:
Notice: Use of RxP without a strong biological filter or without strong protein skimming will endanger invertebrates of all types and can even endanger fish! , (preferred biological method is a bio-ball type wet dry filter. (Weak methods include undergravel, Jaubert, and Berlin methods, the hobbyist is cautioned that these methods may not be strong enough to prevent difficulties). Protein skimmer must be adjusted daily for good foam production! High ammonia or nitrite levels and resulting stress may be experienced with weak biological methods. Product is necessarily strong because marine parasites are hardy, and caution by the user is absolutely required! Do not dose your tank and leave. You must observe the animals periodically during the day.
All Systems: RxP is not recommended for lionfish, stonefish or scorpion fish. Treated fish must be in a reasonably healthy condition for treatment to be effective and for recovery to occur. It is necessary, therefore, to begin treatment at the first sign of infection or even if you suspect infection (i.e. a suspicious spot)! It is recommended that you keep it in stock for immediate use. Skimmer must be adjusted daily for good foam production. The objective of treatment is to have the level of RxP peak immediately when added, then be reduced rapidly by the skimmer (see graphs below). Cloudy water, splotchiness or loss of fish color, excess sliming of corals, tight closing of corals, or corals refusing to reopen within a few hours of addition may indicate overdose due either to poor skimming, poor filtration or overuse. If this happens, use carbon short term and stop use until corrected, do water changes as necessary, or move affected animals. Your reaction to the overdose must be determined by the parameters of your particular system, the severity of the reaction of your animals, and your experience and ability to resolve the problem. RxP is not a dump-it and run type product!
Reefs: Product can be used with most invertebrates by experienced persons, with caution. Since marine parasites are invertebrates, treating them with this product will stress other invertebrates. Use with invertebrates carries a certain amount of risk, however, we at Kent Marine use it with invertebrates on a regular basis because we know what to look for and we can react if a problem develops. If you have expensive hard corals and particularly mushroom anemones, you may want to remove them prior to use to be absolutely safe. If you are willing to accept some risk and closely watch the tank, you may want to leave them in. Use the product with invertebrates at your own risk. Even if you remove hard corals and mushrooms, you will not need to remove the live rock, soft corals, coralline algae etc. and this will save you a lot of time and effort. We find that most soft corals, gorgonians, and star polyps have very little reaction to the product and generally don’t know it is in the water (You should still observe them closely, though). Hard corals react more and mushroom anemones can do well or get hurt fast unless you watch them very closely. Do not ever use with starfish, sea urchins, sea cucumbers, sea apples, medusa worms, nudibranchs or similar animals, you will probably lose them! (Remember, RxP is strong enough to kill free floating ich!)
Some inverts will show sensitivity to RxP use by closing up, sliming, or reacting in other ways. This reaction may be temporary and may not indicate any damage to the animal, but the aquarist must be experienced enough to judge, and increase skimming or use carbon short term to resolve the sensitivity. If in doubt, remove the affected invert to another system! Animals moved in a timely manner will quickly recover from any sensitivity. Animals most likely to have adverse reactions to the product are stony corals and colonial anemones (mushrooms), but carefully observe all inverts. Reactions will vary due to the condition of the system and the animal, but look for "tight" closing of hard corals. This is indicated by the tissue looking as if it has no thickness or being able to see the skeleton shape which is not normally visible through the tissue. Mushroom anemones can react by expelling their internal parts or beginning to get "slimy" evidencing a "melting" condition, if this happens, remove mushrooms immediately. Use of the product with acropora or other small polyped stony corals is not recommended because it is difficult to determine their condition until it is too late. Prolonged use, indiscriminate use, use on weakened inverts or use without proper skimming or strong biological filtration can cause damage or loss. For this reason, use with inverts is at the risk of the user.
Boittom line.....you are going to kill stuff with it.
