A protein skimmer is the hardest-working piece of equipment on most saltwater tanks. It pulls dissolved organic waste out of the water before it breaks down into nitrate and phosphate, which means clearer water, healthier corals, and a lot less algae to fight. But skimmers are also where new reefers get the most confused — the ratings look like a wall of numbers, and “bigger” isn’t always “better.” Here’s a straightforward way to pick the right one.
Do you actually need a skimmer?
If you keep a marine or reef tank with fish and corals, a skimmer is one of the best investments you can make. It removes waste that your filter media and water changes alone struggle to keep up with, and it adds oxygen and stabilises pH as a bonus. Very small nano tanks (under ~40 L / 10 gal) can sometimes get by with frequent water changes, but once you add fish and start feeding daily, a skimmer quickly earns its keep. For dedicated freshwater tanks, skimmers don’t work — they rely on salt to create the fine foam that lifts waste out.
The one number that matters most: your tank volume
Skimmer manufacturers rate each model for a range of tank sizes, and that range is the quickest way to shortlist. The honest rule of thumb: match the skimmer to your bioload, not just your litres. A lightly stocked 300 L tank with a few fish behaves very differently from a 300 L tank packed with large, messy eaters.
- Lightly stocked / beginner tank: choose a skimmer rated at or slightly above your actual water volume.
- Heavily stocked / big eaters / predator tank: size up a model, or pick one rated for roughly 1.5× your volume.
When in doubt, size up a little. An oversized skimmer run gently is easy to dial in; an undersized one running flat-out will never keep up.
Our Mantis Tornado protein skimmers are rated in litres to make this easy — for example the Tornado-120 suits 300–600 L systems, the Tornado-150 covers 500–800 L, and the Tornado-180 handles 800–1,500 L.
How to read the other skimmer specs
Once you’ve shortlisted by volume, a few specs tell you how well a skimmer will actually perform:
- Air draw (litres of air per hour). This is the real engine of a skimmer — more air pulled into the body means more waste contact and more foam. Higher air draw (for a given tank size) generally means stronger skimming.
- Pump wattage. A proxy for power and running cost. Modern DC pumps (like those on the Tornado series) are efficient, quiet, and tunable.
- Footprint and height. The spec people forget — and the one that causes returns. Measure your sump’s skimmer chamber before you buy, including the height clearance to lift the collection cup out for cleaning.
Match the skimmer to where it will live
Most skimmers are in-sump models designed to sit in a dedicated chamber at a specific water depth. Check two things: (1) does it physically fit your sump footprint (and can you remove the cup)? and (2) what water level does it want? Running a skimmer too deep or too shallow is the number-one reason a good skimmer “won’t foam.” If you run an all-in-one tank rather than a sump, confirm the skimmer is rated for your water level — our Rubicon all-in-one reef tanks have a skimmer chamber built in.
Give it time to “break in”
Here’s the part no one warns beginners about: a brand-new skimmer often produces almost nothing — or messy, watery overflow — for the first one to three weeks. The body needs to develop a microscopic film before it skims cleanly, and the pump needs to settle. Don’t panic, and don’t re-adjust it every hour. Set a sensible water level, let it run, and fine-tune once a day. After break-in it should produce stable, coffee-coloured skimmate.
A quick decision checklist
- What’s my real water volume, and how heavily is it stocked?
- Have I measured my sump chamber (footprint and height)?
- Does the skimmer’s rated range cover my tank, ideally with a little headroom?
- Is it a quiet, efficient DC pump I can tune?
- Do I have local support if I have questions?
That last point matters more than people expect. Buying from a Canadian dealer means faster shipping, local warranty support, and someone to ask when your skimmer is in its break-in sulk.
Need a hand picking one?
We’re an authorized Canadian dealer for Mantis, based in Toronto with fast Canada-wide shipping and free local GTA pickup. Tell us your tank size, stocking plan and sump dimensions, and we’ll help you choose a skimmer that fits the first time.
👉 Browse the full range: Protein Skimmers at Fins & Friends
👉 Pair it with flow: Return Pumps and Wavemakers
Questions? Reach us at finsnfriends.ca or (647) 607-7892 — happy to help you build a healthy reef.