Bio media

[viejafish]

Sounds like the guy is trying to get you to spend $$$$. Denser media allows anaerobic bacteria to colonize interior portions of media which help take care of nitrates. Throw it out and you need to find another way to keep nitrates in check. Rinse, yes. Replace, no way!

Your goal is to maintain aerobic conditions for your bio media, not anaerobic. Although there is denitrifying activities in anaerobic media, the rate is too slow to be effective in reducing nitrate to any practical extent in a freshwater aquarium. The outcome is also unpredictable as a shift of the REDOX conditions can generate toxic sulfide. Have you opened up a gunk up canister filter after a power outage and smelled rotten eggs. It's much easier to reduce nitrate with plants or just do large water change.