Hardening sandbed

My sandbed is getting a hard crust on parts of it. It is turning to a dark brown were this is happening. From what i have read this could be from ph or even calcium precipitating out for people who dose. I don't dose yet seeing as I have no coral in my tank. I use aqua vitro salinity brand salt so it should have stable levels. my levels are 0 trate, trite, ammonia, and a ph of 8.0. Any advice or fixes let me know thanks

 

nothing? bump

 

From Randy Holmes-Farley

It is reasonably common to have sand harden, especially when new.

It is not entirely clear whether sand bed hardening is a purely physical process involving calcium carbonate deposition (or other minerals) that cements grains together, or whether it is mediated by bacterial processes, but it does not always happen.

It happens most frequently to new sand, and especially when the pH is high (as when using limewater). It happened to me when I first set up my first tank, but not when adding tanks to the existing system using the same type of sand. I would guess that higher alkalinity and calcium also contribute, as well as lower magnesium.

Often the effect disappears as tanks mature (the hard sections stay hard, but unclumped sand stays that way, and new sand won't as readily clump).
The addition of organisms (cucumbers, etc) seems to delay or stop the process as they keep it mixed up and perhaps break tiny links between grains before they become too established.

 

Sweet thanks for the input

 

also if you google the term "marine diagenesis" or "early marine diagenesis" you should be able to find out more, that is the phenomena you are witnessing.