I was cleaning Mandala's tank today, and well, my siphoner sucked up what looked like black rocks. About the size of a baby snail. I then went to empty out the white bucket that the dirty tank water was in and the "little black rocks" did not fall into the drain with the tank water. So, I reached my hand in there to pick one up and...it turned to goo! It smeared on the bottom of the bucket and my fingers.
What is this stuff? Could it be hurting Mandala?! He has started biting his tail again recently but he does not seem weird other than that.
It was running but pastey, like drying blood or something. But way to big to be blood if it had came from Mandala, as he most likely would be dead.