Jim, I'm new to hydroponics; what do you mean, 'growing media?' You'll be using something that is called 'medium' or 'media' to put the seed into to get it started, and then continue to use that 'medium' or 'media' to support the roots of your hydroponic plant. A medium can be almost anything that will support the seed while it creates a root structure. The medium can be organic (currently living, or was living) or inorganic (it never lived). Some media will add some nutrients and bacterial support to the plant. Some systems might use more that one medium so it may have 'media.' If you watch my Plain 2 Grow Jim You Tube videos, you will see that some of my systems, whether they are active or passive, use more than one medium, or media. The Plain 2 Grow System You Tube channel, in fact, uses multimedia (bad pun)!
The hydroponics purists spit seeds whenever they see a system that has anything in it that remotely resembles soil, or “dirt,” say like sphagnum peat moss pellets or something similar. For the purists, if the roots aren't dangling like a Vegas trapeze artist with no support net, in an approved nutrient fluid, or being sprayed, fogged, or bubbled, then it isn't hydroponics.
Guess what? I've done hydroponics almost every which way, including active and passive, and it comes down to this: If you can start a seed in anything and grow a plant to maturity and fruiting by bathing the roots in a nutrient solution, then by cracky, you are growing hydroponic plants! Period. Don't let anyone tell you you are doing it wrong! There IS NO wrong if you can grow it, admire it, and eat it! Like any advanced hobby, there will be those who spend a great deal of time and money to create the “system to end all systems” that matches their notions of “aqua perfection.” Growing tasty and nutritious foods while conserving time, money, space and resources -and having fun while doing it- should be your goal.
What are the most common media being used by hydroculture growers? Here is a list, in no particular order:
- (U) Perlite and/or vermiculite 2. (U) Coco fiber 3. (U) Rock wool 4. Clay pellets 5. Gravel 6. Brick shards 7. (U) Peat moss 8. Air (U) means I have used it.
I'm going to discuss the media I have used (U) and their advantages and disadvantages. Media I haven't used will get a very general presentation.
I started my very first passive wick plants in perlite, in a system I call the Hydrosock. I use perlite without the vermiculite. In the beginning, the seeds were placed directly in the perlite. I changed the technique later, which I'll discuss a little later in this blog.
Perlite is a “popped” volcanic stone. There are several manufacturers of perlite. It is heated to a high temperature which turns it into a bunch of small white-colored and very light-weight semi-rough spheres. Some soil growers mix the perlite, and sometimes vermiculite, into their dirt to create air space and an even water distribution. It is super-light, very inexpensive, and available nearly everywhere. It has acceptable root support. Perlite wicks well but retains little or no water, which makes it hard to over-water. Perlite will not change the nutrient content or pH of the solution. It creates a great deal of air space in mixed media or by itself. Perlite's worst feature is that it floats on water. I have always had good results with it. Many hydroponics enthusiasts use perlite.
Coco fiber is known by several names: Coco, coco fiber, coco coir, and coconut husk fiber. I have used coco fiber in hybrid systems. I bought a large number of coco fiber baskets on closeout (10 cents each!) and cut strips out of the baskets for my use. You can view the video on my Plain 2 Grow Jim You Tube channel or as one of the videos on this web site. I have used coco fiber mixed in with perlite and I have used coco fiber as a single medium in my Hybrid Aeroponic / Nutrient Film Active System.
Coco fiber is wiry, and while organic, does not rot or absorb water. It wicks well and allows plenty of air space. Coco fiber has pretty good root support. Coco fiber is said to have beneficial bacteria that help plants grow. It can be purchased in many different ways: as small or large blocks; ground up and loose; shredded; and sheets, are just some ways. You can mix coco fiber with perlite and just about any other media. Unless you live near a hydroponics store, or luck up on it like I did, you'll have to order it. It can be pricey. Most hydro growers favor coco fiber over everything else. I'm about even in feelings between perlite and coco fiber.
Hydroponic rock wool is made from volcanic or other minerals and is melted at high temperatures and spun into a fiber. While it is made about the same way as house insulation rock wool is made, it doesn't have the fire-and-mold-retardant chemicals that are added to the construction stuff. I've used rock wool a few times and I wasn't all that impressed with it. It wicks well and holds moisture fairly well. It seems that it would be great for custom shapes and would be the most useful for fitting into small holders and areas. It's features are very similar to coco fiber in availability, types, and pricing. Unlike coco fiber, it does not support a natural bacterial colony. Rock wool is very popular with hydro growers.
Peat moss. Specifically Jiffy brand sphagnum peat moss expandable pellets. I love them! They are cheap and available almost anywhere. They are super-easy to use and almost infallible. You can even get seed starter trays just for them! Okay, here's the rub: The purists will tell you that peat moss is “dirt” or “soil” and as such, disqualifies a system that uses them as somehow “non-hydroponic.” No, peat moss is NOT dirt or soil! Peat moss is partly decayed vegetable matter, hm-mm, say like compost, which some hydroponic growers use to make organic 'nutrient tea.' Soil is composed mostly of minerals with some organic matter mixed in.
The other excuse I was given is that peat moss is too acidic to use in a hydroponic system. That is a chemical issue that is easily handled (see my pH blog). I have had a 97% success rate using peat pellets to start and grow seeds. I use the peat pellet as the upper medium in the HydroSock and perlite as the lower medium. They are an almost perfect combination.
Why does peat moss work so well? The pellet is a moist, warm, and dark environment for beginning seeds. When the roots begin to poke out of the pellet, I just push it into the perlite and cover it. The peat moss pellet has many macro and micro-nutrients. It comes with bacterial colonies. The pellet is full of fulvic and humic acid. Instead of trying to explain fulvic and humic acid to you, go to this link. The downside? It will stain your nutrient solution and perlite. If the solids get into a pump or micro nozzle, it will clog it. Some of the solids will float on the surface of the nutrient solution.
I've never used the other listed media. Air is a big part of aeroponic systems, and it plays a part in my hybrid aeroponic system. However, I do not grow anything that has only root exposure in a highly fogged or sprayed, air-only environment. I'm putting several links below for more information.
There is a great deal of information about hydroponic media I haven't covered. There are many more quality sites like those above. Please do as much research as possible before you commit to a system and the media.