OX2000 mini scuba tank: 2.3 litres, 20 to 25 minutes, worn on your back

The OX2000 is the biggest tank OXSEA makes: 2.3 litres of air, which gives 20 to 25 minutes near the surface depending on your breathing, the depth and the effort. It sits on an adjustable back harness, with an external regulator and a remote gauge you can read while you work.

When the smaller tanks are not enough

• Twin-engine boats. Two outboard legs or two shafts, two sets of anodes, a longer hull. A session that would take three refills with a half-litre tank fits into one.
• Keeping the bottom clean between antifouls. If you look after your own running gear, 20 minutes lets you work at a steady pace instead of racing the gauge. Check your marina's rules first: our guide to cleaning a hull in the water explains why many marinas restrict it.
• Long, slow reef swims. With the OXAIR mask, a Rottnest snorkel trail or a stretch of reef can be done at your own pace. See our guides to Perth and Rottnest and marine park zones for where you can go.

How much air that is

2.3 litres at 200 bar expands to roughly 460 litres of air. A standard 12 litre dive cylinder holds about 2,400 at the same pressure. The OX2000 carries far more than the half-litre tanks while staying a compact tank for shallow water.

Refilling it

The OX2000 pack on oxsea.shop comes with the 12 V / 220 V compressor, which runs from a 12 V battery or mains power. Filling 2.3 litres takes longer than the 12 minutes of a half-litre tank, so start the compressor when you come out of the water and the tank is ready for the next session.

On the boat, run it from the house battery, not the cranking battery, and switch the engine off while it works. Exhaust contains carbon monoxide, and whatever the compressor breathes in on deck, you breathe under the hull. Our article on refilling from a boat battery does the amp-hour sums.

The hand pump cannot fill this tank: it is made for the 0.5 litre tanks only.

Too much tank?

Possibly. If your jobs take five minutes, 2.3 litres is more weight to carry, more time to refill and more air than you need. The OX500Plus and the OX1000 are worn the same way with less. The comparison page helps you decide.

Twenty minutes, same rules

A bigger tank tempts you deeper. Stay shallow, breathe continuously, never hold your breath on the way up and ascend slowly. Fly the Code Flag A (dive flag guide), keep someone on deck who knows when you went in, and in the tropical north read our guides to stinger season and crocodile country first. A mini tank counts as breathing apparatus under fishing rules: see what each state allows.