Im pretty sure that ceramic media is the only thing you should be wary of. The foam can be rinsed as it will very quickly accumulate more bacteria and debris to reestablish it. The reason not to do it on hob filters is that there is not a ceramic colony of bacteria. The surface area of ceramic is so many times more than the foam stuff. When you compare the tiny bit of area in the mechanical media then you have to protect it. It would be beneficial to add an element of ceramic to hobs if you can.
Otherwise clean with aquarium water, or treated water. But do not use the awful filter sludge. :banghead:
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