TW Straight Joint (Green Knob)

The TW Straight Joint (Green Knob) provides aeration for your aquarium.

Key Features

• Increases dissolved oxygen levels for healthier fish
• Quiet operation for home and office aquariums
• Suitable for freshwater and marine setups

Controlling Air Flow with the TW Straight Joint (Green Knob)

This straight in-line joint with a green control knob lets you connect two lengths of airline while dialling the flow up or down. It is the fitting you reach for when one airstone is roaring and another is barely bubbling off the same pump. The knob gives fine, repeatable adjustment so you can balance branches by eye, then leave it set without it drifting over time.

Balanced air really pays off in Singapore tanks. With warm 27-29C water holding less oxygen, you often want a steady, controlled stream rather than a flood of large bubbles that mostly escape. A green-knob valve on each line lets you tune a gentle flow for a betta or shrimp tank, where strong current is unwelcome, while still keeping the surface moving. Fit the valve on the pump side of a check valve so adjustments never expose the line to back-siphon during a monsoon power cut.

It pairs with the rest of our air systems components. See how aeration fits the bigger picture in our air pump guide and our best air pump roundup.