Dave S wrote:

My LFS store has told me that I should change Eheim EhifiMech and
EhfiSubstrat every 8 months. When I asked the reason. I was told that after
a while 'bad' bacteria builds up and it becomes ineffective. If this is the
case, could I boil it (and thereby remove any impurities) and use it again?

Don't boil it, you'll kill all the bacteria and risk an ammonia spike.
Rinse it in the water you remove for a water change every so often to
stop it clogging and you won't get anaerobic pockets where 'bad'
bacteria can sit anyway.

Peter
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