If it is your tank that is leaking bleed it down till its empty and trade it for another one at a welding supply company, or a gas supply. I trade my tanks out instead of refilling them, The tank I bought was beat and looked like it had been used as a hammer at one point in its life, I took it in swapped it out for a filled one, 17 bucks.
29g Tetra Tank
100g Planted Angel/Clown Loach
I can't spell...Im an engineer, I do math