What is this white pasty goo??

[Algae_Farmer]

The past few days I started noticing a few white chunks moving around in the water column. When floating around they look like pieces of white styrofoam, but they are neutrally buoyant. I just realized there are a bunch stuck on the overflow standpipe. I picked one off and it's pasty, best description is it seems like drywall spackle. There is no smell to it and everything else in the tank seems normal. It's possible something fell in, or my kids tossed something in, cuz that's fun right? Anybody ever see anything like this before? I did recently use chemiclean for a minor cyano outbreak but I've changed the water a couple times since then...

 

[Cell]

No clue, but here's a bump for you!

 

[JGT]

Looks like it could be pieces of coral sim to the one near the GSP. Or the kids threw in a half eaten hot dog.

 

[Algae_Farmer]

Right? Most unexplained mysteries in my house come down to kids depositing random items in random places.

The white chunks do look like coral gravel, but they're pasty if you smoosh em (new pic). Seems like a calcium or other precipitate, just can't figure where it would've come from all of a sudden...