A stabilized, gas-infused liquids containing ultra high concentrations of infused gas, produced by: generating a gas-infused liquid in a sealed vessel under a high pressure of at least 20 psi; stabilizing the gas-infused liquid by passing the liquid while still under the high pressure through a tubular flow path arrangement which compresses the infused gas into nano bubbles in the liquid; infusing an additional amount of the gas into the stabilized liquid by injecting the same, while still under high pressure, back into the sealed pressure vessel along with more of the gas; and again stabilizing the liquid by again passing liquid, while still under the high pressure, through the tubular flow path arrangement to thereby form the additional amount of infused gas into nano bubbles in the liquid.