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Hydroponic Grow Media

Hydroponics Grow Mediums

From the reader’s perspective this may very well be the shortest piece about hydroponics on the internet because the mediums used for hydroponic gardening can be summed up in a single sentence:

Hydroponic growing medium can be any inert matter that will anchor the plants.

The topic is a little more complex than one would think and there are many different hydroponic growing medium options available.

The whole idea of hydroponics is that the plants are completely fed by a nutrient solution pumped and recirculated throughout.   The main purpose any growing medium serves is to anchor the plants, so they grow in a stable fashion.

An ideal hydroponic growing medium should not contain any nutrient, trace elements or any other kind of contaminate. The reason for this is that any kind of outside nutrient or mineral is going to throw off the balance of the nutrient solution.

The other thing to consider when selecting a growing medium is water retention. Some inert matter does effectively anchor the plants, but it also holds a lot of water which is going to cause your plants considerable stress from too much moisture.

Old-school methods hydroponic grow media

Back when hydroponics was first beginning with the very simple and old-fashioned wick systems, growers soon released that some sort of anchoring medium needed to be used to hold the plants down.

Most often, back then they used sand or dried clay similar to kitty litter, because this was all new and they had nothing to draw on. The problem that occurred, however, is that these materials are not altogether truly inert.  Sand and clay both contain minerals and trace elements that can and do leach, thus throwing the nutrient solution off balance.

The other problem with these materials is that they both retain a lot of water.

This leaching of minerals, though, is minimal at best, and some amateurs and weekend growers still use them.  I can safely say that few, if any, professional growers still utilize these methods and the methodology has come a long way since then.

River rock

The next stage in the evolutionary development of hydroponic growing mediums was washed river rock.  Normally, these would ½” to ¾” sized pebbles as opposed to the popular 2” landscape stone.

The advantage here is that while river rock adequately anchors the plants without a lot of shifting, it also doesn’t leach any trace elements, nor does it contain any nutrients.

The downside to river rock, however, is that you want to make certain that it has been sterilized.  River rock is called that for a reason, you know, and some of it is derived from water born sources.

The problem is that streams, river and lakes also contain algae which will dry onto the stone. It doesn’t matter how long that dried algae has been out of the water,  once it is exposed to moisture it can come out of this dormant stage and you’ll find yourself with a real mess on your hands.

Nothing can ruin a hydroponic garden more swiftly than an algae attack and especially a nuisance is the string variety which will cling to virtually anything and completely contaminate the nutrient solution.


Perlite, the small puffed white pebbles that resemble Styrofoam and is often used in potting soil, makes an excellent planting medium.  What makes perlite so desirable is that not only is it free of any contaminates it also has a completely neutral pH.

The drawback to perlite, however, is that it is light and tends to float away. Because of this it isn’t a good medium to use by itself.  It also produces a dust when dry that is harmful to human eyes so exercise some caution if you use it.


Don’t let the fancy name scare you off as all growstone made of is recycled glass that has been smoothed through sanding.  Growstone, in my opinion is the absolute best growing medium you can use.

It is 100% inert, pH neutral and will perform the job well while at the same time you’re also helping the environment.  If you’re in doubt as to what medium to use, stick with growstone even though it’s a larger initial investment.

There are no drawbacks that we can think of and once purchased it can be used time and time again and will last you forever.


Rockwool is a spun material made from usually granite and is one of the most popular mediums out there.  It’s completely inert, lasts basically forever.

Although, it is one of the most preferred materials for larger, professional hydroponic growers, I don’t recommend for the beginner or less experienced for a simple reason. Rockwool does retain water and if one is not careful the plants can become supersaturated and the roots can be suffocated.

Over saturation can also cause root rot and other negative conditions you don’t really want to deal with. Another drawback for the beginner is that rockwool will need to be pH balanced before it can be used.

Again, rockwool is an excellent medium but gain a little experience before you switch to it.

There are other hydroponic growing mediums that can be used because there is no shortage of inert materials available.  Some of them would include vermiculite, coco fiber or oasis cubes but I am concentrating on the ones that work well with all six hydroponic methods.

You will want to experiment with some of these options until you come up with the one that works best for you. When it comes to hydroponic growing mediums there is no one-size-fits-all and it all comes down to type of use and personal preference.



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