I'm not familiar with coralcrete specifically, but you can either remove the cup and wait for the effect to go away, or you can keep emptying out the cup and remove whatever it is that's causing it. Think of it as like a water change, because you'll need to replace the water that overfills.
It's hard to say which is specifically the best answer because it depends on the cause. Sometimes you don't want to remove it from the water. Sounds like in this case it wouldn't hurt to remove it from the water, but at the same time it may fix on it's own after a few days.