Sand getting hard

[LakeCityReefs]

Why does the top 1/4" or so of my sandbed get hard and clumpy in some areas?

 

[meir]

I can think of two reasons either there is a buildup of something or there is something living in it but to be sure how abt u post a picture of your sanded

 

[meir]

Sand bed*

 

[Dan1789]

My sand has always done this too. Usually around where the rock meets the sand.

 

[kodo28]

I would say it is normal, due corralline algae being growing on sand.
You can get this solved if you buy some extra cleanup crew for the sand bed like Nassarius Snails or also starfish something like Archaster Typicus

 

[AllSignsPointToFish]

What are you calcium and dKH? Could it be that you're precipitating calcium carbonate directly on the sand bed causing it to clump?

 

[Downbeach]

It could also be something bacteria secrete called "glycocalyx" which forms into a hard rock candy like consistency. I would remove or break up the substrate, and add some Cerith, Nassarius Vibrex snails, or even a Conch if your system is large enough. I would also consider adding this and this, especially if its a DSB.