For divers, the more appropriate term is SCUBA dive tank- one of the greatest innovations in underwater exploration that has allowed literally thousands of divers to go beyond the one thousandth-meter mark. Dive tanks have been invented out of necessity- because human lungs can no longer sustain the body beyond the first few hundred meters. With pressurized and stabilized dive tanks, divers now feel more independent and are able to stay in the water for longer periods of time.
Scuba dive tanks are what divers initially invest in when they decide to go "pro". Diving then becomes more than a seasonal pleasure, because the apparatus is now readily available whenever they need to go deep into the ocean. Marine biologists and amateur explorers owe a lot of their output to well-maintained steel diving tanks that keep the air pressure steady and their lungs filled.
Because the interest in underwater exploration and diving flourished in the last few decades, first time buyers of steel dive tanks can now enjoy a wide assortment of tanks to choose from.
Dive tanks are made primarily with two tough metals: steel & aluminum. Diving tanks or diving cylinders that have been made for extra capacity and increased pressure are often made from steel- the heavy metal is used to buffer the contents of the tank. For lighter explorations, aluminum dive tanks (that are often smaller in capacity, but come in more finishes) are often recommended.
After choosing what kind of material you'd like your scuba diving tank to be, it's now time to decide what kind of pressure you'd like the dive tank to deliver when you're using it. Again, this would be based largely on what kind of depth you're expecting when you're finally out in the sea.
Scuba dive tanks that deliver 2,400 psi are often recommended if the diver is expecting to reach at least 50 feet, to a maximum depth of a 150 feet. Beyond this depth, the tank would find it difficult to deliver the same amount of oxygen due to increased atmospheric pressure.
Very recent developments in scuba tank design have resulted in a remarkable new line of tanks that can deliver more than 3,000 psi. These large diving cylinders are now preferred by veteran divers who are in the water often, and for prolonged periods of time.
One of the most basic queries regarding a scuba dive tank is: should I buy one that has been coated with paint? Or should I buy one that is bare metal?
The answer to this question is really up to you; there's no doubt that the dive tank will suffer from scratches and the occasional rusting after a few years; this is unavoidable. Paints help preserve the surface condition of the dive tank; however, paint cannot really reverse any damage caused by poor care.
If you're still undecided, what you can do is to buy a scuba diving cylinder first that is uncoated, then see if it fares well in that condition before you have it painted.