jplacson:
I was just wondering, why do freshwater divers choose steel over AL tanks? What's the advantage? Doesn't diving in freshwater require less weight than salt water? What's the big advantage of steel over AL? And why do steel tanks have round bottoms, why don't ALs have them as well?
Sorry, these are purely out of curiosity...I've never done any freshwater dives so I was just intrigued by the differences.
You have brought up weighting directly and tank buoyancy indirectly.
When people buy their first tanks, they usually are bargain shopping, so they go with price first, and that usually leads them to aluminum tanks, whether that is a good idea or not.
So absent the pricing issue, you have asked a common question: Which tank is right for you?
Almost all divers require about 4 to 10 lbs of weighting in order to be neutrally buoyant while breathing underwater. Then as you add a thermal suit, the need increases to 6 lbs or more. This pretty much allows you to choose either aluminum or steel tanks, if you please, and then make the balance of your weighting adjustment to the lead on your belt or integrated B/C.
For really warm water, like The Red Sea, at 95F, you probably would be overweighted at the beginning of your dive with steel tanks. For moderately warm tropical water, at 82F, you could probably go either way, with steel or aluminum. For cold water, at 70F or less, steel is probably your best bet.
That also brings up the wetsuit/drysuit issue. If you are wearing a thick wetsuit, you are probably unsafe at depths below 50 ft. However a lot of divers dive deeper than 50 ft with thick wetsuits. Therefore they sometimes try to compensate with an aluminum tank as a band aid. My advice is to avoid diving in a thick wetsuit. Thick wetsuits are cheaper to buy in the short term, although in the longer term you would be happier and better off financially in any drysuit rather than a thick wetsuit.
All other things being equal, I would go with a steel tank, because they last forever, if you treat them right, and keep moisture out of them. But that is not always easy to do, especially on boat dives, where the tank monkey with the air hose is coming around filling the tanks between dives, and he does not do it properly, and he gets moisture into your tank. I have had a steel tank almost ruined that way.