Pull some tank water into 2 bowls or specimen containers. Deep enough to dip just the zoas and plugs.
In bowl #1 add 5 parts tank water, 1 part h202 (a 3% hydrogen pyroxide) and mix.
Can get cheaply at most retail grocers. Usually, less than 5$...
--- dip frags in bucket #1 w h202 for 3 to 5 minutes.
Then thorougly rinse plug or zoa frag in bowl #2 before placing back in tank.
Should take care of sponge or algae and open up in just a few hours and upto 48 hours. Ps. Also will melt zoa eating nudibranchs. A great way to preventatively dip new addition zoas and palys befire adding themnto your show tank.
DO NOT DIP Corals other than zoas or palys in this mix. Lower doses 10:1 ratio can be tolerated by some, but not all other corals.
Zoas and Palys have shown no issues with the first ratio and duration. I've dipped many many this way.
Always wear gloves and be careful with zoas and palys when handling them. Be careful not to get fluids in cuts or eyes. Also, never boil rock with palys or zoas. This can generate a dangerous vapor. Some types may possess palytoxin.
Happy & Safe Reefing !
A.Blake
www.iReef2.com