[GpsFrontier]

Hello twd000,
First even though you have a pH meter, you'll want to get some pH drops. Electronic meters can give false results, even when taken care of and calibrated. pH drops will never give you false readings. Even if you mostly use the meter, you still need pH drops to double check your readings if there is any question about the readings.

Would an NFT or DWC hydro system be more appropriate for these purposes?

You mean systems.... Your much better off growing your crops in multiple systems, rather than one system. Going by your list of plants I would break them into at least two groups. Herbs and lettuce. Then it depends on how many plants of each you'll be growing as to whether I would break them into more systems. The best type of system would depend on the amount of plants, size, and the space you have to work with.

Before you design and build a hydroponic system, you need to know what your designing it for. First you need to do some math deciding on how many plants of each you will be needing to feed your family. As an example, if you wanted/needed to harvest 3 heads of romaine each week, and seed to harvest time is 50-55 days, (8 weeks depending on variety), you'll need to be growing 24 romaine plants at any given time to accomplish that goal of harvesting 3 a week. Since they will be spending about half their life cycle in a prorogation system, the main system will need to have at least 12 spots for romaine lettuce alone. While the prorogation system has another 12 seedlings. Each week you start 3 new ones to replace the harvested ones, and rotate the oldest ones in the prorogation system into the main system after that weeks harvest.

So the first step in designing and building a hydroponic system is deciding on your harvesting goals for each plant you want to grow. Once you know your goals, you can design the system/systems to meet those goals. The second part is knowing how big the plants will be at harvest, and how long it will take to go from seed to harvest. Once you know how big they will get, and how long they will need to be in the system, you can begin to decide what type of system will fit those needs best, and designing it to fit your needs and space you have to work with.

Conventional or organic nutrients?

I know there will be a lot of debate about this statement because there are many diehard believers in everything organic. But when it comes to hydroponics, trying to grow with organic nutrients is not only a waste of time, but much harder to get right. Don't get me wrong, growing organically in soil is very beneficial. But there is one major difference between growing in soil and growing hydroponically. Their is no soil in hydroponics, the very definition of hydroponics is "growing without soil."

Since plants cant absorb the nutrients until the mineral salts are broken down into their raw chemical element anyway, it doesn't mater whether this process is done synthetically, or by microbes, fungi, bacteria, and acids organically. The plant can't tell the difference in how it was broken down. All the plant cares about is that it is broken down into the raw chemical element it can absorb. How it got that way doesn't mater, nor will it make a difference in taste. Since you can't control how fast, or in what amounts the chemical elements are broken down by the microbes, fungi, bacteria, and acids, it just makes it harder to create a balanced nutrient solution, and all for no benefit. So like I said, when it comes to hydroponics growing with organic nutrients is a waste of time, and much harder to get right.

There's still no difference in how the plant absorbs nutrients in soil, or even how they will taste when growing organically in soil. But organic methods are far better for the environment and ecosystem of the ground/soil. A well balanced soil ecosystem can be beneficial for taste as well because it provides a better balance of nutrients (broken down to the raw chemical elements) for the plant to absorb. Any difference in taste isn't due to a difference in the way the plants absorb the nutrients, or how they were broken down, but due to a better balance of available nutrients. Which isn't an issue in hydroponics because a synthetically made nutrient solution already provides a balanced variety of nutrients.

I also run a red worm composting bin - can I use the leachate in a hydroponic system?

Yes, in hydroponics this is known as a compost tea. Which is basically like it sounds, it's a tea brewed using the worm castings (and often other materials) to create a nutrient rich brew of nutrients and beneficial microbes. Compost teas aren't brewed using hot water, that would kill the beneficial microbes, their brewed in a container with an air bubble. The worm castings are typically put in cheesecloth like a tea bag, or straight in and strained out later. Compost teas aren't meant to replace the nutrient solution (though some people try to), but typically used as an additive you add to the nutrient solution. I can post more information about compost teas if your interested.