Time for me to get on my soap box….Aluminum tanks are a poor choice for a primary tank. Yes , the shop you trained at most likely gave you an aluminum tank and only rents aluminums. This is because they are cheaper than steel. (Read the note on steel tanks as to how cheap this is for you)

We recommend aluminum cylinders for Tech divers looking for stage bottles, or argon bottles. They also make great “Pony” bottles for those of you who are required to have them for ocean dives or just want a redundant air supply.

For “Pony’s” we generally recommend at least a 30 cubic foot or large bottle for dives 100 foot or deeper. This will give you approximately 1/3 the air supply of your back gas for most single tank divers. This allows you plenty of time to make your way back to the anchor line or to tie off and shoot a bag.

2015 PSI Cylinder (no boots or valves)
14 cubic foot Part#018 732 $ 89.99

Side note: This is a great cylinder for argon drysuit inflation. Most homebrewers will have a bottle of Argon on hand for drysuit inflation. This low-pressure cylinder allows the home brewer the ability to get a full fill from his 2500 psi Storage bottle. Also, even if the homebrewer only has 1000 psi left in his storage cylinder they will be able to put 7 cubic foot into his argon dive cylinder. This will still allow the diver to get at least two decent dives in from the dive cylinder.

Catalina
3000PSI Cylinders (no boots or valves)