cleaning a canister filter

apolyom

Member
i have a canister filter which is due for a clean. in it i have carbon, bioballs and a filter pad. am i able to change the filter pad to a new one without causing a spike/crash? i have a 100gal with around 40-50kg or live rock.
also is nitrates of 20 ok? obviously 0 is better but is 20 too high?
 
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