I use 1.0264 (35 ppt).
The reason it does not float is because it is tight and dense as it has grown under lower lighting and nutrient conditions. Chaeto under this conditions is darker green, more curly, stiffer and heavier. Higher lighting will make it grow lighter green, more stranded than curly more flexible and lighter in weighit with more tendency to float. Nothing wron with either it is just different environmental conditions.