I’m new to saltwater

[idk what im doing]

I was doing some research and a couple people said this stuff was decaying matter and to remove it so I did but now my dry rock is stained grey? And ideas what it is? I figured I’d add that is feels very sponge like almost holds it’s shape and as I said I’m just lost/confused by it. Also the tank was a 10 gallon but I moved all the substrate and rocks from the previous tank into a 45 breeder the only think I did differently was add a single live rock to the tank?

 

[KrisReef]

It probably was sponge. If it was dead you should have removed it and now that it’s gone it’s left a discoloration on the rock where it was. Oceanic reefs have all kinds of life attached and inside the pores and crevices. That is where the biological filter lives and the life on the surfaces is more diverse than typical freshwater substrates.

Turn the light off to prevent excessive algae growth in a new tank.

Welcome to Reef2Reef!

 

[idk what im doing]

Thank you sm