Cycled Filter Media — Established Lava Rock

About this media

Cycled (seeded) filter media: porous lava rock colonized in a mature, healthy fish tank so it already carries a living nitrifying biofilm. Drop it into your filter — or a media bag where water flows — and you seed ammonia → nitrite → nitrate conversion instead of waiting weeks for blank media to catch up. Honest claim: it jump-starts the cycle. Stock lightly, test ammonia and nitrite, and let the colony grow to match your bioload. Source tanks are clean and not under medication; hitchhikers such as snails or copepods are still possible — we say so up front so you can decide if that suits your setup. This is fish-room media, not bottled “live filter bacteria” and not dry pet-shop rings.

Best for

• New tanks and quarantine / fry grow-out setups
• Breeders who want a faster cycle before stocking
• Anyone seeding a new filter from an established system
• Keepers who prefer real fish-room media over bottled bacteria alone

How to install it

1. Open the bag as soon as it arrives. Pour the bag water into the tank or filter sump — do not tip it down the drain.
2. Rinse nothing under the tap. Tap chlorine/chloramine kills the biofilm you paid for. A gentle swish in tank water is fine if you need to move fines.
3. Put the lava where water flows: a mesh media bag in a canister, HOB, sump, or next to a sponge filter. Sitting on the substrate with no current does almost nothing.
4. Leave it in place. The colony grows to match the ammonia load you give it — seed first, then stock light and test.

After it arrives

After install: stock lightly (or fishless-dose a little ammonia) and test ammonia and nitrite daily for the first week. Zero readings mean the seed is keeping up; spikes mean water-change and add livestock more slowly.

This bag is a seed, not a whole biofilter fill. Keep your normal sponge or ceramic media in the filter too — the lava inoculates them.

Hitchhikers (snails, copepods, etc.) can travel with fish-tank media. If you need a sterile quarantine, say so on WhatsApp before we pack — otherwise treat it as a living piece of a real aquarium.

Go deeper: How to use cycled filter media to jump-start a cycle →