Hobby ceramic air diffuser, 25 or 50 mm
Regular price
$5.00
Regular price
Sale price
$5.00
Unit price
/
per
This Hobby diffuser in porous ceramic turns the air from a pump into fine bubbles, and it can be cleaned with white vinegar when its pores become clogged.
Two sizes: 25 mm cube or 50 mm block, for 4/6 mm pipe.
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The summary
- Which format: 25 mm cube for a small tank, 50 mm block for a longer tank.
- What material: porous ceramic, which can be cleaned with white vinegar.
- For which pipe: standard 4/6 mm airline.
- How to maintain it: a rinse, or a white vinegar soak when the bubbles get bigger.
Fine, lasting bubbles at the end of the air line
The Hobby ceramic air diffuser turns the air from a pump into fine bubbles, which circulate the water from the bottom to the surface and help it take up oxygen. It is available as a 25 mm cube for a small tank and a 50 mm block for a longer tank. It connects to a 4/6 mm air line and can be cleaned with white vinegar.
At the end of an air pump's pipe, the diffuser determines the size of the bubbles. Fine bubbles stir the water from the bottom to the surface and increase the surface area for exchange with the air, which helps your water take up oxygen again. This Hobby diffuser is a block of porous ceramic, supplied in a blister pack, whose nozzle takes standard 4/6 mm airline pipe. It is available as a 25 mm cube and as a 50 × 25 × 25 mm block.
🫧 Cube or block
The 25 mm cube suits small tanks and small pumps. The 50 mm block offers a surface roughly 1.7 times larger, for a stronger pump or a longer tank, where you lay it lengthways. Place the diffuser on the bottom, away from the filter intake, so that the bubbles are not sucked in, and leave its sides clear: buried in sand or gravel, it merges its bubbles into large ones that lose their benefit.
A pump placed below the water level needs a non-return valve
If your air pump is positioned lower than the water surface, water can flow back along the pipe to the pump during a power cut. Place the pump higher than the aquarium, or add a non-return valve on the pipe, between the pump and the diffuser.
Small tub
The 25 mm cube is enough.
Long tank
The 50 mm block lies lengthways.
Pump with 2 outlets
A diffuser at the end of each pipe.
Low-power pump
The cube needs less flow.
A quiet pump for an everyday aquarium
A diffuser is only as good as the airflow it receives. The JBL ProAir silent air pump comes in several flow rates, from 60 to 600 L/h: a small model is enough for a cube or a block in an ordinary aquarium. You get steady aeration without the hum of an oversized pump.
💨 Why fine bubbles
Oxygen enters the water mainly through the surface. Bubbles help in 2 ways: they exchange a little oxygen as they rise, and above all they draw water up from the bottom to the surface, where it is replenished. Fine bubbles multiply the exchange surface and stay in the water for longer, which prolongs this contact. They are also quieter and cause fewer splashes on your lid and lighting than a large, rolling boil of bubbles.
Take your 60 litre aquarium fitted with a small air pump: the 25 mm cube, placed in a back corner, gives a curtain of fine bubbles without stirring up the whole tank. In a tank 100 cm long, the 50 mm block, laid lengthways, spreads the bubbles over a larger area. With a 2-outlet pump, 2 cubes placed at either end circulate the water more evenly than a single diffuser in the centre. The flow is then set with an air valve, so that the bubbles stay fine without splashing.
Over time, limescale and deposits clog the pores of the ceramic: the bubbles get bigger and the pump has to work harder. Soak your diffuser for a few hours in diluted white vinegar, rinse it thoroughly in clean water, then let it dry before putting it back. It will produce fine bubbles again. As it costs little, keeping a spare on hand lets you replace the one that is soaking without interrupting the aeration.
🌱 In aquaponics
In a deep-water grow bed, diffusers placed beneath the floating rafts oxygenate the roots as much as the water. A 100-litre bed of lettuces is well aerated with 2 blocks connected by a T-fitting to a pump of around 150 L/h, placed at either end of the bed: the bubbles run along the roots and stir the whole length, and white, abundant roots show that the aeration is sufficient. The guide to building your own aquaponic system presents this set-up among the others, and the article on looking after your aquaponic system in summer explains why aeration matters even more when the water warms up.
Technical specifications
Both sizes
- Cube
- 25 x 25 x 25 mm
- Block
- 50 x 25 x 25 mm
- Material
- Porous ceramic
- Pipe
- 4/6 mm
To budget for separately
- Pump
- Air pump
- Pipe
- 4/6 mm air pipe
In the box
- 1 ceramic diffuser, depending on the size chosen
Dimensions and material as stated by the manufacturer Hobby, recorded on 13/10/2026.
Manufacturer and product safety
- Manufacturer
- Dohse Aquaristik GmbH & Co. KG
- Postal address
- Otto-Hahn-Str. 9, 53501 Grafschaft-Gelsdorf, Allemagne
- Contact
- info@dohse-aquaristik.de
- Website
- www.hobby-aquaristik.com
Information provided under Regulation (EU) 2023/988 on general product safety.
Which diffuser for your tank?
The same ceramic in two sizes. What sets them apart is the diffusion surface area.
Cube or block?
Answer one question and the table highlights the size that suits you.
| Length (mm) | Typical use | Price | |
|---|---|---|---|
| Recommended 25 mm cubeYour choice | 25 mm | Small tank, small pump | $5.00 |
| 50 mm blockYour choice | 50 mm | Long tank, stronger pump | $6.00 |
25 mm cubeRecommended
What the format diffuses
Length (mm)25 mm
Typical useSmall tank, small pump
50 mm block
What the format diffuses
Length (mm)50 mm
Typical useLong tank, stronger pump
Dimensions recorded on 09/10/2026 from the manufacturer's data sheets.
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Frequently asked questions
6 questions
6 key questions
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