A couple of questions

[tashier]

Just a few questions I had while I was thinking about it.

I believe I have some sponge on my rock. Some yellow, some blueish gray. Sorry, no pics. Is this harmless in a reeftank?

I saw a post that someone lost something to slime disease. What is this and does it spread? What causes it?

Thanks

[Wiskey]

Sponges are usually good, but can be toxic when they die, and don't take well to being exposed to air.

Do you mean brown jelly deise? If so than it's a bacterial thing that turns your LPS coral to this jelly mess, the "jelly" then blows away, and if it hits another LPS coral it starts to take out that one.

Bad news, definitely requires intervention,
Whiskey