Killing sponge

Is there a quick and easy way to kill sponges? I have a black sponge that is slowly taking over my blastos colony.
 
IS there a way to take the whole colony? Sponges don't like air, but coral can be out for a few minutes
 
Can you cover the sponge with epoxy? Then in couple weeks pop the epoxy off or scrape sponge off and cover area with epoxy and pop off in couple weeks
 
1500 magnesium levels for a few weeks will kill it off as well as iodine injected into it.
 
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