Short version? For most tents, get a Rhino Pro sized to your fan and stop thinking about smell for a good long while. Watching the pennies? The Rhino Hobby uses the same RC412 carbon for less, as long as you don't mind flipping it now and then. Want the easiest breathing filter for your fan? CarboAir 50. And if binning a whole filter every year winds you up, the AC Infinity Refillable lets you tip the old charcoal out and fill it back up. One thing before you spend anything, though. Plenty of tents that still smell have a perfectly good filter in them. There's a section on that below.
The best carbon filters for grow tents
Rhino Pro Carbon Filter
The one we'd put in most tents. A 50mm bed of Australian RC412 carbon in a light, aluminium-ended drum, from a little 4 inch right up to 12 inch beasts for big rooms.
- 50mm RC412 carbon
- Anti-bypass design
- 4" to 12"
- Up to 3600m³/h
- Vortex cone base spreads the air about, so more of the carbon actually earns its keep
- Anti-bypass seal stops air sneaking round the carbon and out unfiltered
- Aluminium ends keep the weight down. Your hangers will thank you
Rhino Hobby Carbon Filter
Same RC412 carbon as the Pro, just less of it, for less money. Good for a first tent, or for anyone who'd rather spend the budget on the light.
- RC412 virgin carbon
- Reversible base and spigot
- 4" to 10"
- 9 to 12 month life
- Swap the base and spigot to the opposite end every 8 to 12 weeks and you put fresh carbon to work
- Rhino's own instructions compare this to turning your pants inside out. Crude, they admit. Also accurate
- Keep the washable pre-filter sleeve clean. Spare sleeves are from £6.50
CarboAir 50 Carbon Filter
Handmade in Europe and lab tested by Systemair. The big selling point is the 55.5% open mesh, which lets air through easily without short-changing the 50mm carbon bed.
- 50mm virgin carbon
- 55.5% open mesh
- Washable pre-filter
- 18 month guarantee
- Low resistance, so your fan isn't straining to drag air through it
- Machine-washable pre-filter comes in the box, so there's nothing extra to buy on day one
- Sizes from 4 inch to 12 inch, up to 3850m³/h
Can-Lite Carbon Filter
Can-Filters have been making these for over 15 years and some growers won't touch anything else. 100% Australian activated carbon in a light metal body with a built-in flange.
- Australian activated carbon
- 51% open perforation
- 12 to 18 month life
- Mounts either way up
- Hang it vertically or lay it flat, whichever your tent's frame allows
- Replaceable pre-filter keeps the dust off the carbon
- Can reckon on roughly three harvests before it needs replacing
Phresh Premium Carbon Filter
Australian-mined carbon, and Phresh reckon it'll last up to three years. And it's cheaper than the Rhino Pro on every size we stock in both, which nobody's complaining about.
- Australian carbon
- Up to 3 year life
- 4" to 12"
- Up to 3910m³/h
- The 6 inch x 600mm is rated to 935m³/h, handy if you want headroom without going up to 8 inch ducting
- Goes from a 4 inch for small tents to a 12 inch for proper rooms
AC Infinity Refillable Carbon Filter Kit
When the charcoal's spent, you twist the flanges off, tip it out and refill it with the funnel and scoop in the box. The drum stays. Only the carbon goes.
- Refillable
- 1200+ IAV Australian charcoal
- Rust-resistant steel mesh
- 4", 6" and 8"
- Ships with its first fill already in
- One 8lb refill bag (£36.99) is good for 2+ refills on the 4 inch, or 1+ on the 6 inch
- Dual-layer coated steel mesh, so a humid tent won't rust it out
Why your tent still smells
Before you blame the filter, check the rest of the setup. Carbon only cleans the air that actually goes through it.
Anything that leaks out through a zip, a gap or a loose duct joint skips the filter completely. So a brand new filter in a leaky tent is still a smelly tent. Which is annoying, given what you just paid for it.
- Check for negative pressure. The tent walls should pull in slightly. Bulging out means air is escaping through every gap instead of going through the carbon. Turn the extraction up or the intake down.
- Match the filter to the fan. A filter rated below what your fan moves gets overwhelmed and lets smell through. Compare the m³/h on both, not just the duct size. Not sure what you need? Our fan and filter calculator does the maths for you.
- Seal the joints. Clamp every duct connection properly. A roll of foil tape costs less than a new filter.
- Keep the pre-filter clean. A clogged sleeve chokes the airflow. Wash it or swap it.
- Know when it's spent. Ruled all that out and it still whiffs? The carbon's probably had its day. Humid rooms and long run hours use it up faster.
At a glance
Rule of thumb. The filter's m³/h rating should be at least what your fan actually moves. Bigger is fine. Smaller isn't.
| Filter | Carbon | Sizes | Price |
|---|---|---|---|
 Rhino Pro |
50mm RC412 | 4" to 12" | From £49.99 |
 Rhino Hobby |
RC412, flip the ends | 4" to 10" | From £31.99 |
 CarboAir 50 |
50mm virgin carbon | 4" to 12" | From £58.95 |
 Can-Lite |
Australian activated | 6" to 14" | From £69.00 |
 Phresh Premium |
Australian carbon | 4" to 12" | From £49.00 |
 AC Infinity Refillable |
Refillable, 1200+ IAV | 4" to 8" | From £82.99 |
Prices as at October 2026. Check the product page for the live price.
How to choose
- Small tent with a 4 inch fan? A 4 inch Rhino Hobby if money's tight, the Rhino Pro if you'd rather not think about it again for ages.
- 120cm tent? Most people end up on 6 inch. A 6 inch Rhino Pro or Phresh does the job, and the 600mm long versions give you headroom for hot summers.
- Bigger room, several lights? 8 inch and up. CarboAir, Can-Lite or the larger Rhino Pros, sized to the fan's real airflow.
- Hate throwing things away? The AC Infinity Refillable. Same drum, fresh charcoal.
- Still smells? Read the bit above before you buy another filter.
Not sure what size fan and filter you need in the first place? Pop your numbers into our grow room fan and filter calculator. And if you want the sums explained, our extraction guide walks you through them.
Quick answers
How long does a carbon filter last?
Depends on the filter and the room. Rhino quote 9 to 12 months for the Hobby (with flipping), Can say 12 to 18 months for the Can-Lite, and Phresh reckon up to three years. Damp air and 24/7 running eat into all of those.
Does the filter go inside or outside the tent?
Inside, up high where the warm air collects, with the fan pulling air through it. That keeps the tent under slight negative pressure, which is what you want.
Can I put a 4 inch filter on a 6 inch fan?
You can, with a reducer, but check the airflow first. If the filter's rated well below what the fan moves, the smell gets pushed straight through. Matching sizes is simpler.
Can I wash a carbon filter?
Wash the pre-filter sleeve, not the carbon. Water on the carbon bed does it no favours at all.
Do I need a pre-filter?
Yes. It catches dust before it reaches the carbon and clogs it up. Most of the filters here come with one, and spares are only a few quid.
Still stuck? Give us a ring on 020 8686 9643 or email info@thehydrobros.com.
Or pop into the shop for a natter: Unit 12, Progress Business Park, Progress Way, Croydon CR0 4XD.
More grow guides
- Best pH and EC meters
- Grow tent setup guide
- Grow room extraction: choosing a fan and filter
- What pump for FloraFlex drippers?
- Spider mites: identify, treat and prevent
- How many drippers per plant?
The Hydro Bros Team. We sell this kit and talk growers through it every day in our Croydon shop.
