I had a piece that would not sink. I waited 3 weeks and must not be as patient as you 😀. The way I was setting it in the tank I was able to strategically zip tie some rocks to it and they held it in place. I had to hide one place you could see it with a plant. One note, about 2 months later I had to move it to get another piece out and the rocks fell off. Well, it floated! I reattached the rocks and put it back, my guess it will still float if I removed them. 🤷🏻♂️.