Growing Mediums and Hydroponics
Growing Media for Hydroponic Systems
What growing media with each type of hydroponic system
Its fairly simple to control moisture levels in plants when growing with a drip hydroponic system. If your design has allowed for proper drainage, As long as you design it so it has good drainage, your growing media won’t become soggy. We prefer Coco, Growstone or hydroton in our drip systems, we also add perlite to the bottom of our pots to increase the intervals between drip cycles.
Small starter cubes or small 1 inch baskets are usually best for NFT systems. The idea is to keep the roots in the nutrient stream and avoid allowing the growing media to make continuous contact to the nutrient stream as the medium will become soggy and cause endless plant problems from the bottom up.
Ebb & Flow (flood and drain) systems
The general rule is stay away from any growing media that floats like Perlite, Vermiculite and if not prepped correctly hydroton will tend to float as well. We use Rockwool blocks – 4x4 and a GH Coco Mat. The combination provides great support and the coco mat provides an excellent buffer for pH and over fertilizing.
As with all media, you will need to test out your cycles to ensure that your grow media doesn’t stay too saturated.
Water culture systems
Water culture hydroponic systems don’t require media at all really. The roots are suspended in aerated nutrient solution 24-7. We always use hydroton of growstones when growing in a deep water culture (DWC) hydroponic system.
When growing in a proper aeroponic system we recommend no growing media at all. Your roots should be suspended in the grow chamber using a neoprene collar. There really is no alternative to this method when growing in an aeroponic system.
Wick systems are something we don’t have much experience with when it comes to a true hydroponic grow. You will want to chose an absorbent growing media as the entire system relies on moving water through absorption.
Different types of hydroponic growing media
Rockwool is the most common hydroponic growing media. Rockwool is sterile, porous, non degradable and it’s composed primarily of granite and/or limestone. Rockwool is very absorbent and requires some time to learn, however once you understand your cycles and your environment, you won’t turn back. With rockwool you need to ‘balance’ it before you use it. Soak it in pH balanced water and test it before use.
Grow Rock (Hydroton)
Hydroton is a Lightweight Expanded Clay Aggregate (L.E.C.A.). It’s a type of clay which is super-fired to create a porous texture. It’s lightweight while also providing great support for your plants. Hydroton is non-degradable and sterile that holds moisture, has a neutral pH, and wicks fairly well. Hydroton is reusable, so its very attractive to gardeners on a budget. Hydroton is very popular with hydroponic growers and every hydroponic supplies store carries it.
Coco Fiber – Coco Chips
“Coco coir” (Coconut fiber) is from the outer husk of coconuts. Perceived as the ‘perfect media’. Coco coir is an organic plant material, it decomposes quite slowly, and is seen as a very neutral media from the start. Coco coir is pH neutral, holds moisture well but provides excellent aeration. You can find Coco in coco coir (fiber) and coco chips. The only difference is the size of the media. The coco fiber is fine and similar to soil. Coco chips are like wood chips.
Coco chips allow for more aeration for root systems. Coco fiber does color the water if your media isn’t treated before planting, which turns some hydroponic growers off of growing with coco. Pretreat your coco media with a steady warm rinse and you won’t see much water discoloration if any at all.
Perlite is mainly composed of minerals that are subjected to very high heat, which then expand it like popcorn so it becomes very light weight, porous and absorbent. Perlite has a neutral pH, excellent wicking action, and is very porous. Perlite can by used by itself, or mixed with other types of growing media’s. However because perlite is so light that it floats, depending on how you designed your hydroponic system, perlite by itself may not be the best choice of growing media for flood and drain systems.
Perlite is widely used in potting soils, and any nursery should carry bags of it. However perlite is sometimes also used as an additive added to cement. You may find it for a better price with the building supply’s, and/or at places that sell concrete mixes and mixing supply’s. When working with perlite be careful not to get any of the dust in your eyes. Rince it off to wash out the dust, and wet it down before working with it to keep the dust from going airborn.
Vermiculite is a silicate mineral that like perlite, expands when exposed to very high heat. As a growing media, vermiculite is quite similar to perlite except that it has a relatively high cation-exchange capacity, meaning it can hold nutrients for later use. Also like the perlite, vermiculite is very light and tends to float. There are different uses and types of vermiculite, so you’ll want to be sure what you get is intended for horticulture use. The easiest way to be sure is to get it from a nursery.
Oasis Cubes are similar to Rockwool cubes, and have similar property’s. But oasis cubes are more like the rigid green or white floral foam used by forests to hold the stems in their flower displays. Oasis cubes are an open cell material which means that the cells can absorb water and air. The open cells wick moisture throughout the material, and the roots can easily grow and expand through the open cell structure. While oasis cubes are usually used as starter cubes for hydroponically grown plants, they also have bags you can fill your growing containers with. While oasis cubes are similar to rockwool, Oasis cubes don’t become waterlogged as easily as rockwool cubes. Even so don’t let it stay in constant contact with the water supply, or you’ll still have water logging issues.
Growstone Hydroponic Substrate
Growstones are made from recycled glass. They are similar to grow rocks (Hydroton) but are made of clay and shaped marbles. Growstones are light weight, unevenly shaped, porous, and reusable, they provide good aeration and moisture to the root zone. They have good wicking ability and can wick water up to 4 inches above the water line. So you’ll want to make sure it has good drainage or is deep enough so it doesn’t wick water all the way to the top. Otherwise like with the growing media in any hydroponic system, if the top of the growing media is continually wet, you may have problems with stem rot.