The two main features of this photograph are distinct phenomena. One is that this plant is in re-vegetation. The other is that it's being watered and nutrified hydroponically with a bubble pump.
The former idea's one I got from a co-worker whose dad purportedly grew some excellent weed by keeping the same plants alive. I was, am, and will remain skeptical. But, after 60 days, the plant is alive and new growth is pretty robust. One of the reasons I'm skeptical is, as you can see at top right, little nuisances are ever-present. I don't see a plant going many harvests before the law of averages brings a killing pest or disease. (To be fair, though, I've not experimented with laboratory cleanliness.) Anyhow, cannabis is only "supposed" to grow for one season. This one goes to two.
The bubble pump idea is mine. Bubble pumps are used, rather obscurely, for other applications. But an important part of hydroponic botany is that the roots of any plant need oxygen. This pump satisfies two parameters: movement and oxygenation. The rubber air tube inside the not-too-much-larger plastic tube creates a bubble
that can bloop an adequate flow to a fairly good height - more so the more it's sunk. The pump is on a timer and the water runs over the root ball for a few hours a day. The root ball, in a basket, is the rooting medium.