A new filter is empty of the bacteria (and archaea) that turn fish waste into safer nitrate. Cycled filter media — seeded lava rock from a mature tank — moves a living biofilm into yours. It is a jump-start, not a magic “fully cycled for any bioload” switch — but used properly it cuts the long wait of a fishless cycle and is far more reliable than bag water or bottled bacteria alone.
Porous lava holds biofilm on its rough surface. Ours sits in a mature, clean fish tank until packed wet with tank water and an air pocket for Mon–Wed courier. You get rock plus the gunk that rides with it — that mess is the point. Sellers call this cycled, seeded, seasoned or established media; same idea.
This is different from dry ceramic rings from a pet shop and from factory “pre-seeded” bags. Those can help; they are not the same as media pulled from a working aquarium. It is also not the same as bottled “live filter bacteria.”
The bacteria population matches the load it grew under. After the move it multiplies roughly with the ammonia you feed it. Add a few fish, or a small fishless ammonia dose, and test ammonia and nitrite every day for about a week. If either climbs, do a water change and slow down stocking.
A ~250 g pack is sized as a seed for typical fry, quarantine and small–medium home tanks — not as the only media in a heavily stocked large system. Leave it in; top up with more media over time if your bioload grows.
Media from a fish tank can carry snails, copepods and other microfauna. We pack from mature tanks that are clean and not under medication, but we do not claim a sterile product. If that is a deal-breaker for a shrimp-only or strict quarantine tank, message us before ordering.
Same wet-shipping rules as our live cultures: Mon–Wed dispatch only so the bag does not sit in a weekend depot. Install as soon as you can after delivery.
Seeded / colonized volcanic bio media
Seeded bio media from a mature fish tank — jump-start your aquarium cycle
R100 · ~250 g seeded lava rock
