You can do that, my point is that with mechanical media, you don't need to be concerned about protecting beneficial biology...so you can put those sponges under a power spray with tap water and it's fine. What you want to protect is any bio-media that you have in the last trays. Now in my case, I have all my filters totally filled with sponge material...however, I have a well with no chemical treatment so I clean in my kitchen sink with no issues.When I do the filter clean I always clean the sponges in each bucket of water I take out of the tank for the water change