Floating seems easy when you're lying on the surface of a swimming pool. Keeping your body horizontal seems like child's play.

But when you're strapped down with gear, breathing in huge gulps and trying to maintain a certain depth, all the while adjusting the air flow hoses and valves, it can be quite a challenge!

Scuba tanks can greatly affect your buoyancy and choosing the right one for your trip -- as well as proper positioning on your back -- can make the difference between a hassle and an enjoyable dive.

While buoyancy seems like a simple concept (we add air to our BCD, inhale and float along at what is called "neutral buoyancy"), some novice divers have a hard time maintaining their depth and are constantly fidgeting with the valves and hoses. Sometimes just having the proper tank for your particular diving trip can be a huge help.

Aluminum scuba tanks are the most popular -- possibly because they're cheaper -except in some country like UK where there are the same price-, but also because they're a lot easier to lug around. These lightweight tanks - not lighter than steel but more buoyant in the water for the same size - may require you to carry more weights with you if you wish to descend to greater depths, yet are perfect for those surface and reef dives.

Be aware that most dive shops won't refill an aluminum tank if it is more than 15 years old, so if you plan to keep scuba diving for many years, a steel tank might be a better fit for you. More precisely aluminium cylinders made before 1995 need to be tested every year, it is an electrical Eddy Current Non Destructive Test (NDT). Dive centres will not fill any cylinder not 'In Test'. 

When you're diving in cold water with a thermally insulating dive suit, you're better off with a heavier cylinder made of steel. Actually you need more weigt when using a thermally insulating drysuit, using a steel cylinder helps by not having to put so much lead on your belt. Steel scuba tanks, while they may cost twice as much as aluminum, don't dent easily but the paint and galvanising does chip. Ali cylinders rarely corrode, steel cylinders can have huge corrosion problems by comparison.

A problem with many aluminum tanks is that they can get stripped from screwing on the regulator time and time again. This is not an issue with the steel tank.

Another problem many new divers have with scuba tanks is in the positioning. Did you know that a cylinder placed higher on the back - more obvious with steel tank of course - puts a diver in a naturally head-down position?

Conversely, a cylinder worn too low will leave divers feet-heavy. You can improve your air consumption by placing the cylinder a little higher, just below the head, so that you are naturally horizontal.

You can purchase tanks at 50, 70.2 and 80 cubic feet levels. New divers are advised to purchase either 71 or 80 because they will likely need more air. Larger scuba tanks are harder to find but can still be found for those going on very long excursions. Auxiliary or pony tanks hold 10-40 cubic feet of air and are strapped onto the larger tank for backup.

Scuba tanks need to be inspected every five years, by law in the United States. In Europe, the mandate is every two years. Many divers feel comfortable testing their scuba gear every year, as you can never be too safe when it comes to your underwater breathing apparatus.

Scuba tanks are a large investment initially, but they should last for many years and many breathtaking trips.
WorldDivingReview.