The hardware for these is expensive, it looks like it is a medical tank which have different regs. Just grab the tanks from home depot, there cheap and easy to use
It's called a post style valve! You would need a regulator made for it and use .5 liters per min. flow! The only thing is if do not have a prescription for the use of the cylinder you are breaking the law! This is a Medical gas cylinder and regulated by the FDA!!!!
You can use it for aeration. You will need to get an o2 reg. I got a 5 lpm one, which has a setting for .25 lpm. You need a key to open the valve or just use a wrench. To fill it you need a script.