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⚙️ Filtration

How do I set up a new aquarium filter?

Set up a new aquarium filter step by step — load the media in the right order, prime it, position the outlet, then cycle the tank before adding fish.

The short answer

Setting up a new filter is four steps: load the media in the right order, prime it so water flows, position the outlet, then cycle the tank before adding fish. The filter is just plumbing until beneficial bacteria colonise it — so the real work is patience during cycling, not the install itself.

Step by step

  1. Rinse the media. Give new sponges and bio media a quick rinse in dechlorinated water to wash off dust. Never use tap water on already-colonised media.
  2. Load in order. Mechanical first, biological second, chemical last, following the flow direction. See what order should filter media go in.
  3. Prime it. Fill the canister or hoses so the pump doesn’t run dry. For canisters, see how do I prime a canister filter.
  4. Position and power on. Set the outlet to give gentle surface movement, plug in, and check for leaks and steady flow.
Tip: seed the new filter with mature media from an established tank if you can. A squeeze of an old sponge or a scoop of used bio media hands over a ready-made bacteria colony and slashes your cycling time.

Then cycle before fish

A new filter can’t process waste until bacteria have grown on its media — usually 2–6 weeks. Run it, dose an ammonia source, and test until ammonia and nitrite read zero and nitrate appears. The full method is in how to cycle an aquarium, and what is biological filtration explains why it matters.

Choosing the right filter

If you’re still deciding on a filter, read how to choose an aquarium filter and compare the best external aquarium filter, best internal aquarium filter and best hang-on-back filter — or start at the aquarium filters hub.

Frequently asked questions

Do I need to cycle a brand-new filter before adding fish?

Yes. A new filter has no beneficial bacteria, so it can't process ammonia yet. Cycle the tank first — over a few weeks the bacteria colonise the media. Adding fish to an uncycled filter risks a toxic ammonia spike.

Can I speed up a new filter with media from an old tank?

Absolutely — it's the best shortcut. Squeeze an established filter's sponge into the new one, or move a handful of mature bio media across. That seeds the bacteria colony and can cut cycling from weeks to days.

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