Spreader mats are used to spread water evenly across all channels. More than one layer will slow the water flow and restrict root growth
You'll notice some grooves at the bottom of your Grodan cubes. Make sure that you line them up with the flow of water. Roots will then grow along the planting channels.
It’ll compete with your roots for oxygen, warm your roots and cause all kinds of other problems.
To prevent this from happening, make sure that no light can leak past your Correx cover. You can replace your Correx cover whenever you need to.
If you turn it off, your root tips will quickly dry. You’ll end up with lots of cell damage and dead root mass. Your plants will also begin to wilt very quickly.
When you turn your pump back on, you’ll be flooding dead material with your nutrient solution. This can lead to root diseases and Pythium taking hold - just look at the picture of roots - you don't want that to happen.
Rather than turning your pump off completely, to regulate your flow, turn it down to a trickle when plants have just been transplanted. You can then slowly turn the water flow up when plants are rooting well.
It may be worth buying a spare pump in case the one you've got fails.
Also, if your roots aren't developed enough, your rockwool blocks will soak up too much water, leading to over saturation - some plants never recover from this.
To prevent this, before transplanting to your NFT system, establish plants and air prune roots in 3 - 4" Grodan Rockwool Transplanting Cubes, placed on a mesh shelf.
When roots begin to emerge out the bottom of your rockwool cubes, they hit the air. The root tip dries, forward growth stops and roots start branching off inside the block. Plants will develop a bigger, healthier, more efficient root network.
You know you've got a good root base when lots of root are poking out the bottom of your rockwool block, like tiny little teeth.
At this point, you can transplant them to your NFT system - they'll take to it much faster, and there will a much lower risk of over-saturation.
When you establish plants, you’ll also need to use a propagation light – a 2 tube T5 propagation light or CFL in a propagation tent is a good option.
In NFT systems, your nutrient solution is already very aerated (thanks to the pump). If you need to aerate your tank as well, make sure that:
A) YOU'RE USING THE RIGHT NUTRIENT SOLUTION
Some feeds aren’t designed to be aerated – nutrients will precipitate out of your solution, at which point they’re no longer available to your plants.
AVOID anything that uses organic ingredients, such as seaweed and molasses.
These kinds of products are biologically active and don’t respond well to the oxygen in your nutrient solution - they become oxygenated.
B) YOU LOWER THE STRENGTH OF YOUR FEED
All that oxygen enhances nutrient uptake. To ensure you don’t overfeed your plants, lower the strength of your nutrient solution.
The exact strength depends on what you’re growing, your environment, how hard your water is and other factors.
If you’re using filtered water, you can often go as low as 12 - 14 CF (1.2 – 1.4 EC).
A nutrient thermometer
A nutrient heater
A nutrient chiller