In general terms…
In the market you can find a lot of tank manufacturers, and the specifications for their tank pressures, dimensions, and capacities are constantly changing and provide you several different options. You can choose between scuba tanks manufactured from aluminum or steel. Dive tank pressures span a wide range; however, the most common pressures are “low” (2400 to 2640 psi), “standard” (3000 psi), and “high” (3300 to 3500 psi).
Tanks are also available in different selection of capacities. Tank coatings fall into three general classifications: painted, galvanized, and uncoated. So, as you can see, the options are numerous, and today, we have selected one type of tank for you to start getting prepared for your next purchase. Keep in mind that there is no perfect tank for all diving conditions and all divers.
Nitrox divers are usually limited because of the volume of their tank since they use to stay down into the water by longer periods. Nitrox divers usually push the air limits right to the edge because they have the advantage of the additional time margin granted by the Nitrox. For this type, HP100 is very popular among sport Nitrox divers.
Remember that in the U.S., federal law prohibits the dispensing of pure oxygen at pressures over 3000 psi in DOT-3AL type cylinders. Recently, the DOT has interpreted this regulation to include oxygen enriched air Nitrox mixtures. So, in the case you want to dive with Nitrox, you should avoid selecting high pressure aluminum scuba tanks. Note that this concern does not apply to high pressure steel cylinders, depending on the service pressure of the scuba cylinder it may be filled with oxygen up to a maximum of 3500 psi.
Finally, try choosing a high-pressure steel tank size that meets your needs when it is under filled, putting an end to short fill concerns. If you do not have much money, then aluminum initially costs much less. If using aluminum, avoid paints, and choose the brushed finish. You should choose a convertible valve having a 200-Bar DIN outlet with K insert, often described as ‘Pro DIN/K’ valve. The standard aluminum 80 with a K-valve is not a “one-size-fits-all” tank. Do not forget that selecting the right tank can improve your diving enjoyment!