When growers are referring to it, they're talking about the high strength peroxide from the hydro store. Talk to them about it, and make sure to mention how many gallons your res is, and what your intended purpose is. Some people use it to prevent or to reverse root rot, some for extra oxygen. I only use it to clean my system between turns. It's much safer to get an oxygen pump and an airstone from any pet store for fish tanks.
If you do buy and use the high strength stuff, be careful, it burns your skin if it gets on you, and it's not pleasant.