I start virtually all my plants from seed in a medium called Horticubes. These are small foam cubes that hold moisture and the root structure as the seed germinates and starts to grow. I like the cubes because they allow you to plant lots of seeds in a small space, the cost is reasonable (about 4¢ each in volume, 6¢ each in smaller quantities) and plants grow well. After a seed is placed in the small hole in the cube, just water once a day and give the seedling plenty of light. No nutrients are required in the very early stage. Depending on the plant, it will take 3-10 days to germinate.
I use sheets of the cubes in a large tray with an automatic watering system. For smaller volumes, use only as many cubes as you need and watering by hand probably makes sense. The plants in the cubes stay in the sheets for about 2 weeks. Then the sheet is broken into individual cubes.
For most of the DWC hydroponic systems, I then place the cubes in a 2” net cup to hold the plants in place in the pipes. For the NFT system, the cubes are placed directly into the NFT channels.
One of the fun parts of hydroponic gardening is experimenting with new varieties of plants to grow in your system. There are dozens and dozens of different types of lettuces to grow. My go-to seed source is Johnny Seeds because of their vast variety and quality of their seeds. Also, I tend to get pelleted seeds as these are much easier to handle and worth the added cost, in my opinion
Some of my favorite varieties:
• Salanova - Green Butter, Red Butter, Green Oakleaf, Red Oakleaf
• Rex Butter
• Coastal Star (Romaine)
• Basil - Genovese
• Five Star mix
Plants grown in the ground absorb minerial nutrients that are dissolved in soil as they are watered. The magic behind hydroponics is that the “food” or minerals are directly in the water. But the big question is how much nutrients should be in the water. The pH level, which affects how much of the nutrients a plant can absorb, is also very important.
Fortunately, the nutrient and pH level can be easily measure with relatively low-cost meters. The pH level is rather straightforward as there are lots low cost meters to measure pH. For nutrients, as you add more minerals to water the electrical conductivity - or EC - changes. Some of these hand held meters are very low cost - sub-$20 for both meters. But a good meter (about $200) is well worth the cost to be confident in your pH and EC level. This is the meter I use.
To adjust the pH level of your water, generally you will need to lower the level by adding acid (pH Down) to the water. The ideal pH for green leafy vegetables is 6.0.
Hydroponic nutrients come in a two-part mix - aptly name Part A and Part B. At high concentrations, the minerals bond with each other and need to be in separate solutions. Once they are added to water, they are fine in the diluted form. Be cautious as there are many very expensive 2-part hydroponic liquid nutrients - targeting another cash crop. I get my nutrients for $70 at AmHydro.com and that is enough for 5 gallons of Part A and Part B. That is more than most hobbiest need. There are places where you can get these nutrients in smaller quantities including Amazon.