Sponge?

[Hugowar]

I have had this chartreuse colored sponge looking growth in my tank for about 4 months. At first only a few, now there are about 20. They seem to prefer the underneath (dark side) of rock and vary in size from chocolate chips to almost dime size. Over time their opening seems to elongate. Does anyone have any experience with this or the ability to generally identify it? No harm seems done, but they are multiplying, and now camping on the stony parts of my hammer coral.

[Hugowar]

https://flic.kr/p/W3evzK

[Hugowar]

https://flic.kr/p/X1z3mj

[Hugowar]

https://flic.kr/p/Xgim2z

[Half Vaped]

Looks like a Pineapple Sponge. Nothing to worry about; they come and go depending on nutrient levels.

[Ron Reefman]

I'm no expert, but I don't think that's a pineapple sponge. I've never seen a pineapple sponge that big or one with color. But then I haven't seen a pineapple sponge in many years!

But I do think it's a sponge. Most sponges don't do well at all in marine tanks. A few do and they do tend to like the underside of the rocks. I get yellow ones and black ones that stay completely under the rocks and die off if they are exposed to the light by turning the rock over permanently.

I don't know what that one is or what it will do, but I'd keep a close eye on them. If they are starting to develop on the skeletons of your corals, I'd be watching VERY carefully to see if they have any bad affect on the coral. If they bother the coral I'd probably consider scraping them off or try a very small dose of something like hydrogen peroxide or aiptasia-x in a syringe and inject it into the sponges that affect the corals. My best guess is they will probably bloom and then fade away like so many things do in our tanks, especially new tanks. If they don't die off, you may have your hands full trying to keep them under control.

On the other hand, if they slow down the spreading tendency, having some sponges in the tank is a good thing.

[Half Vaped]

I thought Pineapple Sponges are supposed to be yellow, but I Googled it and I think Ron's right--Pineapple Sponges are more white and have fringes on the tube.

Apparently it's the sponges in my sump that are Pineapples. The yellow sponges I have in the display look just like yours and also prefer the dimly lit, medium flow parts of the rocks. I have a lot and never had any problems with mine bothering corals, since they prefer areas that corals don't thrive in.

My tank is 2.5 years and have never bought any sponge other than what pops out of my live rock. I had red, white and purple sponges come and go. I have a colony of blue sponge that was huge at one point, but has now become a shadow of its former self. But for some reason the pink and yellow sponges just keep getting bigger. Hopefully I can keep those going long-term.