Now hereÂs an interesting point. I was reading some of the posts on soil mixtures and yes that works with a passive system. But suppose you donÂt have all that water and material to waste. And waste water we do. Do you know why we lose it. Because we complete with the sun and wind for it. Think how much moisture you lose thru the exposed surface on those large pots. Then too the large drainage holes across the whole bottom. Used for the express purpose of getting rid of water. The various soil mixes donÂt hold water, itÂs constantly giving it up. So , what perilite holds 80% of the water per volume in each tiny bit. It gives it off at 10% of that volume. What happens when expose to light and wind? It evaporates. I didnÂt say bright sunlight or strong wing. Even shade and a light breeze. You need large supplies of mix to last any kind of time. Hence the large pots. Think on it for a minute...why does our soil become toxic from fertilizer? Because we have to use so much to be certain the plant is getting fed thru all that mix. The roots arenÂt thru out the mix. So each time you fertilize your building pockets that build up and up till the plant starts to die. Ever play a game called pachinko? ItÂs a large flat game with ball bearings at the top. The idea is to release the ball bearings and try to guide them by flippers along the way to the bottom where thereÂs one hole you want them to slip thru. A lot...a lot miss that hole. ItÂs poured out on the floor, evaporates and forms clouds. With an active system the water you put in circulates top to bottom over and over. No motors, no pumps. Just plastic .Air is sucked in by evaporation. Again think of the pichikno game. Instead of one hole to catch the ball bearings, there are many from the top to the bottom. They line the inside walls but not the middle. The middle is devoid of the plants rootÂs, too toxic in an active system. What fertilizer you use is washed over the roots over and over again till the water evaporates thru the only hole it has left. The plant itself. Think of it like the noise maker for New Years. A rolled up paper tube that uncurls when you blow it up. Fertilizer gets used up. This method uses 1/10 the material and a lot less water. Even better for those of you who are handicapped and canÂt lift the weight of 2 or 3 liters you can reduce that weight by a third of volume by using Styrofoam.