I was just wondering if it should be capped as I've heard it turns to dust after a year. It also float around when doing a water change.
It is very light, I don't doubt it will float around during water changes. When I had it I really liked it, but I had to accept the drawbacks of using it.
Yes it turns into dust/muck over time, how long? Depends how much you mess about with it. I planned on having mine a year at max, and at about 6 months it was slowly starting to break down, enough that I could tell anyway. A good way around this is to have a nice carpet of dense plants, and do not disturb if at all possible. I moved the tank, a 4 hour adventure, and when I filled it back up wow, every plant leaf was covered in a dusting of black crap. Some filter floss, 1 week and a 50% water change later and as good as new.
Now after a year, when I broke the tank down, wow, this stuff was almost half powdery muck. But still usable if you do not disturb it, and have a healthy amount of roots holding it together. But I was generally very impressed with it.
At the time I got it, it was roughly half the cost of aqua soil, now (here in Canada anyway) it's basically the same cost, so I won't ever buy it again. The price is what drew me to it before.