fluval 305 filter change

I usually wash my filters in tank water every 2-3 weeks, i dont think it really needs to be replaced but once a year (1 of the 4 every 3 months or so). I wouldnt replace them though unless they get really gunked up and rinsing them in tank water doesnt seem to get them clean. My media baskets (4) have 3 baskets of bio media, and the top basket has filter floss, and that gets replaced/rinsed every 2-3 weeks as well.
 
I have the similar Fluval 405 (4 tray). The recommended schedule is a little generous and you can typically extend the life of all media before replacing them. I rinse out the mechanical filtration about once a week under the tap, but use tank water only for the prefilter (I don't use carbon). I use Clearmax resin for algae control in the lower tray and change that every 2 weeks. The Biomax doesn't get changed until it looks really nasty. The key is to never replace more than one tray of Biomax at a time, and to never run the Biomax under tapwater (kills nitrifying bacteria immediately). I use 2 trays of Biomax substrate. Top tray in my setup is a polishing pad that gets replaced every 2-3 weeks.
 
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