Rockwool vs. Coco Coir & Perlite

I decided to grow four Tokyo Hot chile peppers to full maturity indoors using just high pressure sodium (HPS) lighting -- no sunlight. Three of the plants were eventually transplanted into 5-gallon Smart Pots (a breathable fabric container) filled with a 70/30 mix of Mother Earth coco coir and Perlite. The other plant was grown in a Grodan Unislab—just 304 oz (or 2.375 US gallons) of rockwool measuring just 9.5 x 8 x 4 inches!

My Tokyo Hot chile peppers are going nuts in their ebb and flow table. They get flooded twice a day now—an hour after my lights come on and half way through the day cycle. I am running at around 1.9 - 2.0 ms or 1,000 PPMs on the x500 scale if you swing that way. pH is maintained beween 5.8 and 6.2 and nutrient temperatures stay a pretty constant 68 °F (20 °C). Relative humidity usually lurks around the 50 - 60% zone. Lights off temperatures have dipped below 64 °F (18 °C) which has caused the plants to go into generative mode—i.e. flowering and fruit production. Yay!

The Tokyo Hot chile pepper growing in the Grodan Unislab is doing as well, if not outperforming, those grown in 5-gallon Smart Pots filled with a 70 / 30 mix of coco coir and perlite

Okay—but here's the real eye opener for me. All the plants are doing great. You can see that. But the one in the foreground is doing especially well. It's got more fruit on it than any of the other three plants.

Green Tokyo Hot chile peppers growing in coco coir in 5 Gallon Smart Pots and Grodan Unislab

It's just dripping with chiles! The production is incredible! So what's with this plant?

The answer is pretty simple. It's growing in rockwool. A Grodan Unislab to be exact. But here's the kicker. There's only 304 oz of rockwool in a Grodan Unislab. That's just 2.375 US gallons! Whereas the plants growing in a 70 / 30 mix of coco coir and perlite are languishing in nearly 5 gallons of growing media. They're also in Smart Pots—awesome fabric, breathable containers—so it can't be said that I'm neglecting them. All my plants are getting the royal treatment!

Beautiful thick main stem of Tokyo Hot chile pepper growing in a Grodan Unislab

As you can see, the main stem is just as thick (and beautiful) as the others. Now, Grodan don't actually recommend putting Unislabs (with a Gro-Block on top) in ebb and flow systems as they say that the trays rarely flood high enough, but mine does, mainly thanks to the 50 gallon reservoir underneath.

Incredible growth in such a small amount of growing media--thanks Grodan!

Seriously—I can't believe that a plant so big can grow in so little growing media. I believe this is a testament to the immense growing power of rockwool. It can hold on to so much air and water at the same time, and gives up moisture when drying out almost as easily as when saturated. It's pretty amazing stuff—and you thought it was just good for insulating your attic, eh? (Actually that's fiberglass—completely different stuff!)

Tokyo Hot chile peppers, ripe and ready for harvest

It's easy to spot when these Tokyo Hot chile peppers are ready to be harvested! And boy, are they delicious or what! They aren't too hot and have a beautiful, deep, distinct and earthy flavor. I love them—and just as well, because I don't exactly have a shortage!

The four plants are currently lit with a single 600W HPS in an Adjust-a-Wing Avenger reflector. The plants are starting to outgrow their footprint, but rather than add another light, I'm going to acquire a LightRail light mover and increase my footprint the smart way!

An even canopy is so important to get right when growing indoors

The canopy is nice an even, mainly thanks to some soft mesh netting (that you can no longer see) which helped to spread out the plants and keep them squat and relatively low.

My nutrient mix for full fruit production is pretty simple:

Reverse Osmosis water—the only way to start any hydroponic nutrient solution! I love starting at zero PPMs!
CaliMagic by General Hydroponics - up to 300 PPMs 
Flora Series by General Hydroponics - one part GROW, two parts MICRO, and three parts BLOOM
Floralicious Plus, also by General Hydroponics
Diamond Nectar, also by General Hydroponics

In fact, this is a very "General Hydroponics" orientated formulation! I use all the additives as directed on the manufacturer's label.

The pH is a little low—around 4.7—so I add hard tap water at the end (10% tap water to 90% reverse osmosis) which helps to bring the pH up to around 5.8 to 6.0—ideal—I also find this helps with pH stability too.

Obviously my nutrient solution is well aerated thanks to an air-pump and airstone.

If anybody wants seeds from this beautiful plant, hit me up! I'm happy to send wherever you happen to live. Peace and happy growing. Everest.