Don't use straight 3%. Please use these dip charts that Justin Credible made. I have used them on many of the corals in this list with great success. I am bringing a goni back to life from massive alage take over that I plan to post on one day.
H2o dipps are FANTASTIC for killing alage off.
# DIP Charts
Tolerance
Dip 5 minutes Milliliters of Hydrogen Peroxide 3% to Liters of Seawater Type of Cnidarian
Low 20-40ml Acropora (tolerance varies widely among species), Montipora, Astreopora, Duncanopsammia, Turbinaria, Galaxia, Cyhpastrea, (*Alveopora)(**Hydnophora) Echinophyllia, Mycedium, Oxypora, Tubastrea,
Low/Med 50-70ml Pocillopora, Seriatopora, Stylophora, Caulastrea, Clavularia, Pachyclavularia, Sympodium, Cespitularia, Yellow Leathers, Pachyceris, Echinpora, Leptoseris, Pectinia, Psammacora
Medium 80-120ml Porites, Xenia, Brown Leathers, Pavona, Fungiids, Heliofungia,
Med/High 130-200ml Goniopora, Favia, Favites, Goniastrea, Platygyra, Leptastrea, Blastomussa, Cynarina, Physogyra, Plerogyra, Symphyllia, Sinularia, Corallimorpharian (Mushroom Anemone)
High 210-350ml Zoanthids, Palythoa, Scolymia, Acansthstrea, Micromussa, Lobophyllia, Euphyllia, Catalaphyllia, Trachyphyllia,
Coral can be dipped longer in a lower concentrate solution. ¼ concentrate for up to 20 minutes for deep, persistent algae or bacterial infections, or necrotic areas.