Power filters should be cleaned about once a month. However, if the filter is less than 6 weeks old, do not clean it because you can upset the good filter bacteria.How often do you wash out filter media, also how often do you change the media?
To clean the filter, wash or squeeze the filter materials/ media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn.
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If your having a problem with ammonia due to the tank still cycling, just reduce feeding to once every couple of days, and do a 75% water change and gravel clean the substrate 4-8 hours after feeding.
After the filter/s have settled, you can feed them every day and do a 75% water change and gravel clean the substrate once a week.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.