Pool filter sand turning blackish color?

[cheryldooley]

I have three tanks that have sand as substrate before it was gravel but changed to natural look... Any way. I'm wondering why my sand is turning kinda black? It was pure white till I did my water change and noticed wth vacuum it's dark and black in spots. Why does that happen?! Is something wrong?

 

[wildroseofky]

It is a build up of organic matter. Dead plant roots, fish food, and other stuff builds up and turns the sand black. You can just stir it up and vacuum it out when you do a water change. It is a good idea to stir the sand when you do a tank cleaning. Lots of stuff can get trapped in the sand.

 

[cheryldooley]

Even if I stir up every couple day and a vacuum clean once a week? Ok thanks. I'll try and fix it somehow

 

[wildroseofky]

Plant matter is the most common culprit. I have up and switched to black sand. White sand is just too hard to keep clean. When I took my light colored sand out there was massive patches of black with root strands in it. I routinely poked around in the sand to keep gas pockets down and I think it just pushes all the poo and stuff into the sand and causes these black pockets. Strangely, when I switched to the Black Diamond Blasting sand the gas pockets were never a problem again. I never do the sand stirring and poking in my tanks now and have never seen a gas bubble pop out of the sand.