This tanks been up over a year but the black sand is new, it was added about a month ago. I tried it out in my betta's 2.5 gallon planted before putting it in this tank, it's still black and clean in there after six months so I we went ahead and switched this one over.
Honestly it looks really nice in person and there's no fish in the tank, just a couple hermits and if it starts looking icky I'm going to siphon some out and add more, I still have half the bag. Although I recommend a good rinsing, we rinsed it out until the water ran clear and it still turned the tank black for a few hours, I stuck in a sponge and some carbon and it cleared right up.