Welcome to ScubaBoard, where some of us are always confused, welcome. At the top of each page is a button "Forums" click here and watch the diving world open up. It's better than walking into a dive shop. The early listings of topics are devoted to questions about diving instruction, and questions about how to start. . . Now comes the good stuff. There is a large section about every piece of equipment a diver can take underwater, don't forget to continue down through the topics. There are areas for local clubs. . . there are areas to travel within the United States. . . and all over the world for diving.
As for your immediate question, all diving tanks hold filtered air. How much, how long the tank will last, and how versatile, these are all variables. Inside the U.S. a tank must be approved by the DOT, the department of Transportation, for construction and safety. Aluminum, steel and fiberglass wrapped steel, are all legal for holding high pressure air. There are different prices, and advantages and disadvantages with each choice.
Worldwide the overwhelming number of SCUBA tanks are the aluminum 80 cubic feet. There cost is low, and they last a long time with care. If you go to a diving resort that's probably what a resort will offer for the lowest price. There are some people that want a smaller lighter tank, and there are some people that want a bigger heavier tank. . . they are all available for more money.
As a new diver, rent your gear at first until you can find if you have a personal need for something that will cost more. An empty aluminum 80 has no more appeal than an empty beer can, and can be recycled. A high pressure (higher than 3000 psi) stainless tank has no more appeal than an empty beer can and can't be recycled, cost effectively.
Hi could someone help me. I just started to get in to diving and it been very confusing, I would like some help on tanks I'm getting lots of answer.As a bigginer should i buy steel tanks or aluminum. 
