Hydroponics is the most renowned hydroculture system where plants are grown without soil and instead using water and essential nutrient solution. Rockwool is the most accepted hydroponic growing medium because it has excellent water retention features, aeration, and porosity, malleable.
They are mostly famous because of their ideal water retention ratio and aeration ratio. It is highly capable of holding moisture and can retain a minimum of 18% of air space.
Since it has porous and fibrous nature, it can also drain excess water. This promotes a significant optimal growth of the roots. But, they are very expensive, and most people cannot afford it; hence, it is important to find rockwool alternatives for hydroponics.
Common Rockwool alternatives include coco peat, perlite, rice hulls, sand, rock salt, oasis cubes, sponges, etc.
Why is Rockwool Considered the Industry Standard for Hydroponic Systems?
To understand why Rockwool is preferred for a hydroponic system, it is important to know some insight about Rockwool itself. It is a mineral fiber insulation widely used in the construction industry.
It is a chemical combination of slag by-products and volcanic rock that is further melted and spun into fibers.
Because it is a breathable material, it allows moisture and air to pass through it. Hence this is the reason it is preferred in the horticulture process. It allows the roots to optimize, which initiates excellent growth of the plant.
If you want to start your hydroponic gardening with seeds, Rockwool is the best medium to begin with. The ratio of water retention and aeration is perfect in it. It can store adequate moisture and allows a minimum of 18% of air space, which helps in the excellent growth of the root.
The notable characteristics of Rockwool are it is porous and full of fibers. This feature helps a lot to drain excess water while simultaneously storing it, considering the amount of moisture at the bottom of the plant.
The roots can permeate through the Rockwool system, thereby absorbing the entire nutrient-rich water. This feature immensely helps the seeds germinate and let the plants grow in full bloom.
Another important feature of Rockwool is that it can be easily cut and given any shape despite any setup and size of hydroponic gardening. The Rockwool material can be very easily inserted into a net cup. They can even be used again by simply mixing the previously used Rockwool with diluted bleach.
Because of these very simple and effective characteristics, they are extensively used in the hydroponic system by experienced professionals. They are extensively used to grow flowers, melons, lettuce, peppers, strawberries, and herbs.
What are the Shortcomings of Rockwool?
The main disadvantage of Rockwool is that it isn’t environmentally friendly. Though durable, they cause a huge environmental nuisance because they do not biodegrade. Though they are great for plants in hydroponic gardening, they harm human health.
So if you are using Rockwool in your hydroponic gardening, it’s always advised to take precautionary measures. If you have asthma or are allergic to dust, it’s better to avoid them. Because in the new blocks of Rockwool, lots of loose dust fibers can seriously affect your eyes, mouth, skin, and lungs.
Since Rockwool has high pH, the nutrient solution needs to be continuously adjusted to accommodate this, which badly affects the pH levels in your system.
Since they have high water retention capacity, it will result in a restricted root environment and low buffering for water and nutrients. Hence the water flow in the root system is hampered though the water content is high.
10 Trusted Rockwool Alternatives for Hydroponics
Rockwool in hydroponic gardening is an expensive procedure that many people cannot afford. Moreover, they are quite difficult to find also in many areas or if you are on a tight budget.
So Rockwool alternatives for hydroponics are highly acceptable by most people as they can be found easily at any density and size as per your need and are safe for your health as well.
These alternatives also work excellently as a growing medium in hydroponics. Below list will showcase some of the Rockwool alternatives.
Coco Coir/Coconut Fiber
Coco coir is made from the husks of coconut fiber. Since they are hydrophilic, they absorb water very easily. When these are exposed to hydration, they usually form a gel-like substance.
They are an excellent medium to germinate seeds and work well in netted pots. They are biodegradable in nature and don’t cause root rot or fungal issues.
The disadvantage of coco coir is that they are not ideal to use alone and often need to be mixed with nutrient solution to avoid inundating the plants as they contain potassium and phosphorous.
Perlite works excellently in a hydroponic system as it doesn’t hold any moisture. Due to this, there is less chance of overwatering, adding more oxygen to the roots.
Due to this feature, the roots of the plant always remain in the water or are usually wet.
They mix very well with other gardening mixes hence very popular in hydroponic. However, one challenge you would face with perlite is that they only work excellently in soilless mixes.
Sand is one of the oldest hydroponic gardening mediums but is very seldom used.
Sand works excellently in drip irrigation methods because it can filter very quickly without holding any hydration for prolonged durations. They hold water for much longer than soil or gravel.
However, sand is not much used as they dry out very easily and has no nutritional value to impart to the plants. So you need to frequently water the plants. Further, it is salty and alkaline, which needs to be washed very well with acid before using for hydroponics.
Rock salt in hydroponics is not used to a huge extent, unlike other alternatives. They are mostly used for aquatic plants where the salt tolerance level is quite higher than others.
Salt doesn’t have any link with the growth of the plant, but they are used for treatment.
However, if the water source has a huge amount of sodium, then rock salt should definitely not be used for hydroponics.
Oasis cubes are used widely for seeds, seedlings, roots, and even transplants. These cube forms are made from phenolic foam, a water retentive and soil-less growing feature.
Therefore, they are ideal for hydroponic gardening and very versatile. They have no impact on the pH level and can be reused to grow lettuce, tomatoes, etc.
However, their biggest disadvantage is that in the case of large plants, they are not enough and need an additional medium like LECA or soilless mix. They are not natural as, well.
Sponges are widely used to germinate seeds in a hydroponic garden. Since they are hydrophilic, they absorb water easily and hold high nutrients.
This benefits the roots immensely. So all you need is to place the seeds in the sponge and soak them in water and cover them and put them away from light.
After a short span, the seeds will sprout. The only disadvantage is that they don’t fit in large net pots.
Clay pebbles are hugely preferred by many because they are very affordable and last quite a long time in the hydroponic system. They are also hydrophilic like sponges, absorb water very easily, and hold high nutrients.
Being versatile, the roots always get better nutrition for growth. Their disadvantage is that they don’t have any nutritional value and need frequent watering as it has no water retention.
Rocks and Gravels/Sandstone/Growstone
The rocks and gravels, Sandstone, and Growstone are a mixture of rocks, gravel, sand, rock salt, clay balls, perlite, or pumice and vermiculite in proper ratios to use in hydroponic gardening.
They have great drainage features as they have very high water retention, and the plants don’t need soil to grow.
They can also be reused to grow hydroponic plants and are very eco-friendly. They provide good oxygen to the plants and are not expensive. The only disadvantage is that they should not be used to germinate seeds.
Vermiculite is a renowned medium for hydroponic gardening made from a water-retentive and soilless growing medium caused by the immense heating of a rock.
They are available in different sizes and are versatile for pots of different sizes.
They can hold water excellently and quite more than perlite such that sometimes it clogs the systems and can wick it upward. They are often combined with other soilless growing mediums like moss or coco coir to generate an excellent result for growing hydroponic plants.
It also improves moisture-holding capacity and drainage in any soilless medium and is affordable. Vermiculite is always advised to use with a combination of other growing mediums instead of using it alone for hydroponic gardening.
Rice Hulls are a great alternative to perlite and vermiculite in hydroponic gardening. Rice hulls are also hydrophilic.
Absorbing water very easily and holding high nutrients. So the roots get all the nutrients because they are highly adaptable.
They are generally the by-product that comes from rice production, so they are a natural and compostable medium. Gardeners highly prefer them as they can use in a soilless mix as they are sustainable and green.
Even carbonized rice hulls are highly preferred as they are rich in macro and micronutrients. The only con is that it performs best when it is blended in to mix properly.
Frequently Asked Questions (FAQs)
Is Rockwool safe to use?
Yes, Rockwool is safe to use. As they have dust and fiber, they are not much good for the lungs, but scientific results involving magnetometric evaluation declared that the Rockwool particles that were inhaled are not responsible for causing immense lung toxicity. At most, it will irritate your skin and eyes during physical contact with coarse fibers and dust.
Is Rockwool better than Coco?
Rockwool is always better than Coco because they insulate more than coco. Hence, it is always an ideal choice for plants that grow better in cool temperatures. Coco is better for plants in well-aerated growing conditions as they suffocate and compact roots quite less than Rockwool. The pH level of Rockwool is neutral, whereas coco is slightly alkaline.
Rockwool is a great choice of growing medium in the hydroponic gardening system. However, they are not the only option. This article has covered other alternatives to Rockwool to use in the hydroponic system.
Moreover, Rockwool is a bit expensive, which might not be the budget for everyone. Hence these alternatives are very affordable and extremely environment friendly. So choose any one of them as per your needs.
Finally, Happy Gardening!!!