Sponge and flatworms?

[Weboh]

In my tank, there's something that looks like a sponge that's been growing a long time. Today, I saw a bunch of flatworms in it. I didn't think I overfed enough to support that big a population, but it looks like the sponges have turned into a breeding ground for the flatworms. Are they eating it? Is it actually something they built? Should I do by best to get rid of the sponge (if that's what it is)? See pictures. Thanks.

 

[Oldreeferman]

That is not flatworms,
You have a bit of a Bristleworm infestation but they are harmless CUC.
Probably due to overfeeding & leftover food in the tank. Take care to only feed just what the fish will eat & no more & when the food goes down eventually so will the worm population. Removing them would probably make the nutrient issue worse let them consume what is left, just get stingy while feeding.
The sponge is a good filter feeder just leave it be also.

 

[Timfish]

De Goeij's research on sponges has shown cryptic sponges on reefs convert Dissolved Organic Carbon (DOC) and Dissolved Organic Nitrogen* (DON) released by corals, fish and algae into Particulate Organic Carbon (POC) and Particulate Organic Nitrogen (PON) aka detritus which can then be fed on by animals such as bristle worms. Be carefull cuttin back on how much you feed your tank. Depending on whether your bristle worms are eating left over food or actually feeding indirectly off what your corals, fish and algae are releasing into the system reducing how much you feed may have a negative impact on you fish and corals.


*DON includes amino acids and urea which will not show up on our tests. Ammonia, nitrate and nitrite are all Dissolved Inorganic Nitrogen (DIN)

 

[Weboh]

De Goeij's research on sponges has shown cryptic sponges on reefs convert Dissolved Organic Carbon (DOC) and Dissolved Organic Nitrogen* (DON) released by corals, fish and algae into Particulate Organic Carbon (POC) and Particulate Organic Nitrogen (PON) aka detritus which can then be fed on by animals such as bristle worms. Be carefull cuttin back on how much you feed your tank. Depending on whether your bristle worms are eating left over food or actually feeding indirectly off what your corals, fish and algae are releasing into the system reducing how much you feed may have a negative impact on you fish and corals.


*DON includes amino acids and urea which will not show up on our tests. Ammonia, nitrate and nitrite are all Dissolved Inorganic Nitrogen (DIN)

Huh. My fish do usually eat practically everything I put in there. The only thing I may have a little extra of is phytoplakton and Reef Chili to feed the coral. It's possible the sponge is just eating the excess, but I feed way below the recommended dose of Reef Chili, and the plankton is live...

I guess I won't worry about it knowing both of these things are harmless. Some people pay for sponges and have a hard time keeping them alive, and I accidentally brought a whole colony alive. Go figure.