Red worm poop??? What are these hard little pebbles around the mounds? Pics included

[Badblackdog]

The brown pebble sized things. I pulled some out and they are hard as a rock. If anybody has a clue help me out.

 

[tzabor10]

Looks like larger sand particles. Try removing them and examining under magnification

 

[Badblackdog]

Looks like larger sand particles. Try removing them and examining under magnification

Thanks for the suggestion. I will try that. This is a used tank with the existing sand bed so it could be anything.

 

[tzabor10]

Thanks for the suggestion. I will try that. This is a used tank with the existing sand bed so it could be anything.

I have mixed size as well. It creates an uneven pattern.