Please help to identify Gray in sand

[Cooperdoodles]

I have a 36 gallon bow tank. Fully cycled 9 weeks old so very young. I even have copepods. I have good circulation in every area but front left. This is where the gray accumulated under the sand deep and on top.

I just did a 5 gallon water change and siphoned the bottom. All was looking good but this morning it’s back. Will better circulation in that corner take care of it? See photos.

 

[AllSignsPointToFish]

Looks to me like you're using silicate sand, not aragonite. My guess would be that it is stratification in the different minerals that the silicate sand is composed of (unless I'm misinterpreting the photographs). If it is gray matter on top of the sand, it could just be an accumulation of detritus in an area of lower flow.

 

[Cooperdoodles]

This is the sand I use. It isn’t detritus I have a great CUC and this is after I cleaned it up anyway. So it needs to be something else. It is located in the area that has the least circulation. Thanks I appreciate you responding.

 

[Is this the LFS]

This is the sand I use. It isn’t detritus I have a great CUC and this is after I cleaned it up anyway. So it needs to be something else. It is located in the area that has the least circulation. Thanks I appreciate you responding.

Are you able to vacuum that area up to get rid of the grey?

 

[Bryan68]

I can't help with your sand issue, but I like your tank!

 

[my.PsychReef]

Looks like the issue is with the type of sand in the tank. Unlike freshwater, saltwater requires aragonite based sand. That sand does not look like for marine aquariums.

 

[Cooperdoodles]

If it’s the wrong sand why would it only be in one area? I can carefully change out sand next big water change in about a month if that would help

 

[AllSignsPointToFish]

That sand is probably composed of a number of minerals with difference densities. The more dense minerals will tend to congregate in areas of lower flow....kind of like those gold mining shows on TV where the dense gold concentrates in stiller areas of water flow.

 

[Is this the LFS]

If it’s the wrong sand why would it only be in one area? I can carefully change out sand next big water change in about a month if that would help

Because if it is indeed deposits and other minerals from the sand, it would make perfect sense because it is all gathering into the low flow area. If you do change the sand, look into caribsea. They are my number 1 choice

 

[Cooperdoodles]

Thanks I will do that. The sand was cleaned but maybe there is a mineral that just changes color when compacted. Crazy thing for sure.