[gmkcpa]

I'm using a Carlile CC burner and I have two 2R oxy tanks. After renting for a few years I bought them. A refill costs $20 + tax & hazard stuff of about $2.50, so $22.50 to refill each tank. The 2R is the biggest oxy tank you can get. I can make 7-8 marbles with a tank (I think-I never counted and wrote it down; 7-8 marbles is the minimum-maybe I get a few more out of one tank). It takes me about an hour and a quarter to make a marble (I'm new at it; I've made only about 100 marbles so far).
When you rent the biggest tank it has a different designation (I forget what it is). Once you buy it they call it a 2R.
The oxy gauge should maintain the pressure for a few hours after you turn the tank off (if you don't release the pressure, like some people say to do). If the tank pressure goes down significantly within an hour, I'd guess you've got a leak.
I can pretty well judge when the tank pressure gets low if I have enough gas or not to make another marble. If I don't think I have enough oxy I start making beads and pendants until the gas runs out and I switch tanks.
Colors? Maybe you need a lot of pressure on the tourch to get them. I've heard that you don't get much pressure from an oxygen generator. The oxy gauge on the tourch side I usually keep set at a low of 25 psi and a high of 35 psi.
Finally, even though I get my vortexes to go straight and deep, make cool flowers and love making 'matrix marbles' with silver fume, I'm pretty much self trained (thank the heavens for the 'how to' articles in GlassLine). The reason I really like this forum is I get feedback from other peoples posts. So, if you got feedback, lay it on me.