Short version? For a small tent, get the AC Infinity Cloudforge T3 (£72). It's a 4.5L smart humidifier with humidity and VPD triggers built in, so it switches itself on and off. Bigger tent? The AC Infinity Cloudforge T7 (£169) does the same job with a 15L tank and 1300ml an hour. Watching the pennies on a room up to about 3m x 3m? The Sonic Air 10L is £74.95. And for a proper grow room, the Sonic Air PRO (£299) pushes out 6.5 litres an hour and tops itself up from a tank. Whichever you buy, feed it RO or distilled water.
The best humidifiers for grow tents and grow rooms
AC Infinity Cloudforge T3 Humidifier Gen 2 (4.5L)
The one we'd put in a 60 or 80cm tent. Small tank, smart brain. It reads the humidity through a corded sensor probe and works to a humidity or VPD target on its own, no extra controller needed.
- 4.5L tank
- 10 mist levels
- Humidity and VPD triggers
- UIS compatible
- EC ultrasonic vaporiser with ten levels, so you can nudge the humidity rather than fog the tent out
- Flexible tubing stretches to over 4 feet, which lets you aim the mist where it's needed and away from the light
- Timers, a backlit display you can switch off at night, and auto restart with memory after a power cut
- Shuts itself off when the water runs out
AC Infinity Cloudforge T7 Humidifier Gen 2 (15L)
Same smarts as the T3, much bigger lungs. A 15 litre tank, up to 1300ml an hour, and up to 30 hours between refills. The one to look at once you've outgrown a small tent.
- 15L tank
- 1300ml/h
- 46 dBA
- 100W
- Humidity and VPD triggers plus timers on board, ten mist levels
- Two nozzles in the box: an elbow for aiming at one spot and a five-way head that spreads the mist about
- Sealed body and waterproof ports, so a splash near the controller cable isn't a drama
- Hidable display and auto shut-off when the tank's empty
Global Air Supplies Sonic Air 10L Humidifier
The workhorse. Ten litre tank, up to 800ml an hour, and Global Air say it suits rooms up to around 3m x 3m. Not bad for under seventy-five quid.
- 10L tank
- 800ml/h
- 4 directional spouts
- 1 year guarantee
- Fully adjustable output, so you can turn it right down for a tent
- Four spouts on top. Point them about the room, or cap a couple to send the mist where it's dry
- Auto shut-down when the tank runs empty
- Works with plug-in humidity controllers
Global Air Supplies Sonic Air 23L Humidifier
For people who are sick of refilling. A 23 litre tank, up to 1.44 litres an hour, and it's on wheels, which you'll appreciate once it's full.
- 23L tank
- 1440ml/h
- 110W
- Can run from a reservoir
- Filler lid on top, so you can top it up with a hose instead of taking it apart
- Adjustable output and automatic shut-down
- Can be hooked up to a tank so it refills itself (see below)
Global Air Supplies Sonic Air PRO Humidifier
The big gun. Up to 6.5 litres an hour through a 6 inch spout. There's no tank to babysit, because it plumbs into a header tank and tops itself up through a built-in float valve.
- 6.5L/h
- Internal float valve
- 300W
- Replaceable discs
- The spout turns through 360 degrees, and you can run it into ducting to put the mist exactly where you want it
- Overflow valve, drain plug and a low water LED, and it switches off when the water runs low to protect the discs
- On wheels. Handy, as it weighs 9.35kg before you add water
- Can be run from the GAS Enviro Controller v4 (£295) if you want the whole room on one box
Faran HR-15 Humidifier
A commercial-style unit that connects to any water source, ideally an RO filter. Covers grow rooms from 15 up to 30 square metres.
- Up to 30 m²
- Up to 500cc/h
- Mains or tank fed
- 310 x 310 x 470mm
- Plug it in, connect the water, set the dial. Not much more to it
- Sturdy and easy to carry about
- Pairs with Faran's own humidistats for proper on and off control
Want the humidistat too? Buying them together works out cheaper. The HR-15 with Analogue Humidistat is £345.00, which is £8.99 less than the analogue hygrostat (£59.99) bought on its own alongside. The HR-15 with Digital Humidistat is £419.00, £36.99 less than adding the Faran Digital Humidistat (£161.99) separately.
Shop all grow room humidifiers
What to fill it with, and where to put it
Every humidifier here is ultrasonic or close to it. They shake water into a fine mist, and they don't care what's dissolved in it.
So fill one with hard London tap water and the minerals go airborne too. You get white dust on the leaves, on the lights, in the carbon filter. And the discs scale up and lose output. On the Sonic Air range, tap water voids the warranty as well. RO or distilled, every time.
- Measure first. Stick a min max thermometer hygrometer in the tent for a day or two so you know how dry it really gets.
- Aim the mist away from the lights and the canopy. Wet leaves are not the goal. Damp air is.
- Put something in charge. The Cloudforge units sort themselves out. A plain humidifier wants a controller, like the Inkbird IHC200 (£38) or a Faran hygrostat, or it'll mist all night.
- Keep the sensor out of the fog. Mount it at canopy height, away from the spout, or it'll read 90% and switch off far too early.
- Go easy in late flower. That's when you usually want the humidity coming down, not up. Our dehumidifier guide covers the other side of it.
Other humidifiers and bits we stock:
The RAM 5L is the cheapest way in. 400ml an hour from a 5 litre tank, 30W, and a knob to turn it up. Fine for a small tent, as long as you put it on a controller.
At a glance
Smart ones manage themselves. The rest are cheaper per litre but want a controller.
| Humidifier | Water | Max output | Control | Price |
|---|---|---|---|---|
 AC Infinity Cloudforge T3 |
4.5L tank | Not stated | Humidity, VPD, timers | £72.00 |
 AC Infinity Cloudforge T7 |
15L tank | 1300ml/h | Humidity, VPD, timers | £169.00 |
 Sonic Air 10L |
10L tank | 800ml/h | Manual, controller ready | £74.95 |
 Sonic Air 23L |
23L tank or reservoir | 1440ml/h | Manual, controller ready | £164.95 |
 Sonic Air PRO |
Header tank | 6.5L/h | Manual or Enviro Controller | £299.00 |
 Faran HR-15 |
Any water source | 500cc/h | Dial, humidistat ready | £294.00 |
Prices as at November 2026. Check the product page for the live price.
How to choose
- Small tent, 60 to 80cm? The AC Infinity Cloudforge T3. Or the RAM 5L on a controller if money's tight.
- 120cm tent or bigger? The Cloudforge T7 if you like the AC Infinity app, the Sonic Air 10L on a controller if you'd rather keep the change.
- Fed up of refilling? The Sonic Air 23L with a float valve and tank, or go straight to the Sonic Air PRO.
- Proper grow room? The Sonic Air PRO or the Faran HR-15, both fed from a tank or RO supply.
- Just cuttings? A lid on a propagator does most of the work for nothing. Our propagator guide has those.
Read the water bit above before you fill anything up.
Quick answers
Do I need a humidifier in my grow tent?
Often, yes, especially in winter. Heaters and extraction dry the air out, and young plants and cuttings like it damp. If your hygrometer keeps reading low, a humidifier is the fix.
What humidity should my grow tent be?
Global Air suggest 70 to 90% for propagation, 50 to 70% in veg and 40 to 50% in flower. Other makers quote slightly different ranges, so treat these as a guide and check your plants.
Can I use tap water in a grow room humidifier?
Best not. Ultrasonic humidifiers put the minerals into the air along with the water, which leaves white dust everywhere and scales the discs. On Sonic Air units it voids the warranty. Use RO or distilled water.
What size humidifier do I need for a grow tent?
For a small tent, a 4.5L unit like the AC Infinity Cloudforge T3 is plenty. The Sonic Air 10L suits rooms up to around 3m x 3m. Bigger rooms want the Sonic Air PRO at 6.5 litres an hour or a Faran HR-15, which covers up to 30 square metres.
Can a humidifier refill itself from a tank?
Some can. The Sonic Air PRO has a float valve built in, so it just needs a tank and a hose. The Sonic Air 23L needs a float valve adding first. The Faran HR-15 connects to any water source with a fitting kit.
Do I need a humidity controller with my humidifier?
For a plain humidifier like the RAM 5L or Sonic Air 10L, yes. A plug-in controller such as the Inkbird IHC200 or a Faran hygrostat switches it on and off to hold a target. The AC Infinity Cloudforge T3 and T7 have humidity and VPD triggers built in.
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 dehumidifiers for grow rooms
- Best grow room heaters
- Best EC fan speed controllers
- Best clip and circulation fans
- Best grow tents by size
- Grow tent setup guide
The Hydro Bros Team. We sell this kit and talk growers through it every day in our Croydon shop.
