What's happening to my Substrate?

[NanaReefer]

Was looking for my Emerald Crab in my sump where I discovered my substrate is as hard as a rock. Mainly around the edges.
So I checked the DT and found a spot in a corner where it too is hard.
What's going on and how do I fix this?

 

[mfinn]

I remember something about this from years ago.
Something to do with added calcium and aragonite substrate.

 

[mfinn]

After thinking about it for a while ( have to do that a lot these days. lol) I remember it was with deep sand beds that I had a problem with the substrate turning into concrete.
I think it was the calcium bidding with the aragonite substrate.
I think the only solution was more sand sifters and cleaning regularly to break up the action.

 

[NanaReefer]

After much research I found it to cause no issues. So as long as it's just my fuge I'm not gonna worry about it. Like having LR for substrate-lol. So far my DT is fine. The small area I just broke it up

 

[rafity]

Looks like a happy and safe DT then.