Rockwool Plug 75x75x65mm – Cultilene · Professional Hydroponic Substrate

The Rockwool Plug 75x75x65mm is the professional standard for the intermediate vegetative phase, a high-quality inert substrate designed to guarantee a root ball capable of absorbing nutrients efficiently and supporting vigorous growth.

Is rockwool really as difficult as they say? There is a lot of noise in the forums. Some say it alters the pH uncontrollably, others that it dries out too fast, and many beginners avoid it because they believe it is a material reserved only for industrial experts or laboratory scientists. This misinformation often leads growers to choose lower quality substrates or, worse, to use rockwool without the necessary preparation.

The result of this confusion is usually fatal for the plants. If you don't treat the block correctly before putting your clone in, the alkalinity of the rock will block nutrient absorption. You will see yellow leaves, stunted growth and you will think "this product doesn't work", when in reality it is just a matter of protocol. Using this material without adjusting the parameters is like trying to drive a Ferrari with diesel: you are going to break the engine before leaving the garage.

The solution is simpler than it seems: knowledge and a quality product. This Cultilene block is designed to offer the perfect balance between water and air. By following the simple steps of stabilization that we explain here, you turn a "difficult" material into the most efficient, clean and controllable home for your roots. This description is your guide to stop fearing hydro and start mastering it.

Typical myths about rockwool substrates

• Myth: Rockwool is toxic to plants. Reality: It is an inert material made from basalt rock; it is sterile and free of pathogens, safe for your crop.
• Myth: You can use it directly from the package. Reality: It is essential to soak it in water with adjusted pH (around 5.5) for 24 hours to neutralize its natural alkalinity.
• Myth: You have to squeeze it to drain the water. Reality: Never squeeze it. If you compress it, you destroy the internal structure of fibers that hold oxygen, suffocating the roots.
• Myth: It is only for large automatic systems. Reality: It is perfect for home growers looking for precision, whether in Hydroponic and Aeroponic Systems or manual watering.

What this product really does (and what it doesn't)

The Rockwool Plug 75x75x65mm acts as a biological "gym" for your plants. Its main function is to provide a sterile and structured environment where roots can expand rapidly without the resistance of compacted soil. By having a vertical fiber structure, it guides root growth downwards, preparing the plant for a stress-free transplant to a slab or a larger pot.

What this block does not do is feed your plants by itself. Being an inert substrate, it has a nutrient charge of zero (EC 0.0). This is a huge advantage for the technical grower, as it gives you absolute control: the plant eats exactly what you give it in the irrigation. However, it means that you cannot neglect fertilization from day one.

Advantages and benefits when used properly

• Total Nutritional Control: Being inert, it does not interfere with your fertilizer program. If you add a BAC Root Stimulator, you know the plant receives 100% of it.
• Superior Oxygenation: Even when wet, it retains a high percentage of air, preventing root rot better than compacted soil.
• Stress-Free Transplanting: The 75x75x65mm size is standard. It fits perfectly into the holes of cultivation slabs, making the step to flowering immediate and safe.
• Cleanliness and Hygiene: Forget about mud and pests that often come in low-quality soil bags. Rockwool is clean and sterile.
• Water Efficiency: It retains water incredibly well, allowing you to space out irrigations if you manage the humidity correctly.

Tips to choose well according to your expectations

This block is ideal for you if you are looking for precision and speed. If you are a grower who enjoys measuring pH and EC and wants to maximize the yield of every watt of light, rockwool is your best ally. It is the standard in the Dutch industry for a reason: it offers consistency.

However, if you prefer a "natural" style of growing, where the soil buffers errors and you don't want to worry about pH meters, you might prefer organic soil. But if you have decided to take the leap to Cloning and professional growing, pay attention to this:

• If you expect fast growth, combine this block with a drip system.
• If you expect simplicity, remember to stabilize the pH of the block the day before. That is 90% of the success.
• If you are going to transplant to soil later, you can use this block, but make sure to bury it completely so the wool doesn't dry out.

Frequently Asked Questions

How do I prepare the block before use?

You must submerge the blocks in water with a pH adjusted to 5.5-5.8 for about 24 hours. This lowers the natural pH of the rockwool (which is usually 7.0 or higher) and prepares it for the roots.

Can I reuse these blocks?

No. Once the root system has colonized the block, it is impossible to clean it without destroying the structure. It is a single-use product to guarantee sterility and performance.

Does it fit in the hole of the rockwool slabs?

Yes, the 75x75mm size is the standard dimension designed to fit into the pre-cut holes of most cultivation slabs on the market.

Can I use it for organic farming?

Although the material is mineral, you can use organic fertilizers. However, rockwool is usually used with mineral fertilizers to avoid clogging the drippers and to take advantage of the precision of the substrate.

Personal Experience of Pevgrow’s CEO (Alan)

I've heard all kinds of horror stories about rockwool: that it burns plants, that it's impossible to stabilize... In my experience, all those problems come from the same mistake: treating it like a sponge. I've seen people wring out these blocks with their hands until they leave them dry. That destroys the air bubbles and turns the block into a brick.

When I use these Cultilene blocks, my ritual is sacred: a good soak at pH 5.5 and I never, ever squeeze them. I just let the excess water drain by gravity. The rooting speed I get with this method, especially when moving cuttings to the growing room, is superior to any peat pellet I've tried. It's not magic, it's just physics applied to cultivation.