Before you go and purchase an HPA tank there are a few questions you first need to ask yourself. The very first question being how much are you willing to spend? If you’re not wanting to spend a lot of money then you’re probably better off buying an aluminum air tank. If you don’t mind spending a little more though and want to get the absolute best compressed air tank possible then I would recommend going with a carbon fiber tank.
The next question you need to ask yourself is how long of an air tank do you want to buy. Most paintballers will want to stick to a 68/4500 as it is the best tank size for the average player. If you’re a little shorter though then maybe a 45/4500 would be good for you. Or maybe a 50/4500 if you like the style of the peanut tank.
Bigger players can of course use one of the larger sized tanks such as 88/4500. And if you have a stock on your marker and are using a remote coil to attach the tank to your back then an 88/4500 will also work great as well.
I would also recommend using this calculator to help you decide which tank you buy based on how many shots per fill you can expect to receive using a particular sized tank. This video from Hustle Paintball will also help give you a visual reference of the different sized tanks you may want to buy.