I do not rinse stratum. It is a low nutrient, clay based susbtrate. I bought it on release day (1-2 yrs) and only got rid of it a month ago. Did not turn to powder at all.
The way to use stratum is like this:
1. pour the dry soil into your tank.
2. spray it with water with a spray bottle and mix it at the same time
3. contour it however you want
4. Do planting.
5. Put a paper plate down and then fill VERY slowly like only a trickle of water until you get like 3-4" on top of the substrate then you can start filling faster.
To be honest I had better success with stratum then eco comp.