To add on to Reefer_peter, I place my siporax in an egg crate so that I can shake it to remove build ups:
But I’ve had it for more than 1 year in my sump already and so far i’ve never need to shake it
I’m currently using marinepure in conjunction with siporax
Marinepure
Pros:
1. Very porous
Cons
1. Crumbles easily
2. May clog
Siporax
Pros
1. V porous
2. Wouldn’t clog at all (if placed correctly) due to the cylinderical design
Cons:
1. Relatively more expensive
More info on siporax:
https://www.ultimatereef.net/threads/aac-siporax-is-back-i-kid-u-not.744707/
Hope that helps