I purchased a hammer coral from live aquaria’s divers den and it’s been doing really good, opened up real nice but i just saw this as i was looking at my tank. Is this brown jelly disease? If so how can i treat it? Thanks guys!
It's difficult to confirm from this photo, but it does look very similar to the brown jelly I had in late 2018. I'd recommend removing that coral from your tank before it has a chance to spread. I lost about 25% of my corals as it spread before I realized what it was.
If you have access to a microscope, take a look at a sample of the jelly under magnification. Here's a video from a sample from my tank during the outbreak, showing the ciliates filled with zooxanthellae consumed from the corals.