Tomatoes can tolerate a wide swing of nutrient levels. I've grown sweet peppers in the sames system as eggplant without any problems. I typically start the solution with an concentration around 450ppm. Tomatoes I normally start the batch around 700ppm.
I don't know if a sweet pepper is more akin to hot peppers than bells though.
I grew wax peppers ( a bell variety) several years ago but they were by themselves. It didn't seem they needed a particularly high EC, but back then I didn't know as well what I was doing.

Depends on variety. Some hot peppers grow really large and fast. They will use more nutrient. Plus, a lot of hot peppers produce a lot more fruits than bells. We're talking a difference of 10 to 1 and higher. I grow jalapenos with bells. Last year I grew those and eggplant in one system. All performed very well with EC around 1.4 to 1.8. I'm not incredibly strict (some would just say I get lazy).

Thanks for the input. Based on your alls PPM/EC levels. I think I may have been running the EC a little high in the past for the bell peppers. I did notice the difference in production levels (10 to 1 or more for spicy to bell), but in addition to getting less the bell peppers stayed small and never seemed to fully ripen or get sweet even when they turned color. It could also be due to temperature or the fact I did not prune the peppers well and suspect I let too many flowers develop at once.

I am going to split the tomatoes into a different system this year and see if I get better results. Then maybe I can figure if it was the nutrients or something else I need to correct. Thanks again.

I started Bells & Chilies in the same system about a month ago. There both doing quite well. The only problem I can foresee is that one type may start growing faster than the other, depriving the slow growers of light. In a system with long runners and/or adequate spacing and appropriate lighting this shouldn't be a problem.

hardclay makes a good point. I suppose I should point out that my peppers are all grown outdoors in the sun where such things aren't as much of a consideration.

I don't grow tomatoes with peppers (anymore). They have different nutrient, temperature, and watering requirements. Can it be done? Sure. Am I doing hydro to get mediocre results at a high price. Absolutely not. I suppose the question is in whether you are doing this for hobby or to grow food at an affordable price and know what it has on it. My reasons are a little of both, but my business side makes me obligated to optimize for net worth, which I'm still working on in the field of hydro.

We all have are own specific reasons for doing hydro. And mine are some of both, better food and at an affordable price (as well as others). But out of those two I opt for affordable every time. If it's not economical to grow it isn't really worth it to me. I also grow outside so lighting isn't really an issue for me.

For me it simply isn't economical to build a different system for every plant I want to grow. If I want to grow 6 crops, that's 6 different systems I need to build, including 6 different pumps, reservoirs, timers, etc. and all the related parts. Thankfully I grow outside so I wouldn't need to buy 6 different lights as well. For me combining plants is quite useful and economical. If I can grow the same 6 different crops, but in only 3 different systems, that significantly cuts down on the cost to grow them in the first place. That significantly "increases" my return on investment (ROI).

So a slightly lesser quality plant is acceptable for me. To get the same return on investment with twice the build cost, they would need to produce much more produce to justify added expense (even if you can taste a difference). But that doesn't mean that I wouldn't try to make improvements if I could. Weather it be in system design, efficiency, growing conditions etc., but it would need to be economical for me to implement. Even if a bell pepper I grew tasted ten times better than anyone else, it wouldn't be economical if it cost $12 to grow.

When I'm at the grocery store I look at the produce that costs the most, as well as what I spend the most money on. Then I decide if I use enough of it to justify dedicating space in a hydro system, as well as the resources I have to work with to grow it. Then I decide what would be the most economical way to grow however many plants I think I best. Even though I have no problem with combining plants in a hydro system, I would prefer to grow plants together that have similar needs for better results.

Simply speaking, I don't' look at like I'm in a competition to grow the best plant possible. I look at it like will it save me money to grow it compared to buying it from the store in the long run. Simply growing my own plants and allowing the produce to ripen on the plant is a vast improvement in taste and quality over store bought produce where they pick the produce green, just to keep it from getting soft before it reaches the customer.

Another reason I grow hydroponically, is because the soil here in the desert is so bad for growing plants. Growing in hydro is more economical as well. By the time I bought all the materials to build a raised bed, soil amendments etc., I could have easily built an economical hydro system to grow the same (even more) plants. Another reason is the ability to control the growing environment, allowing for growing out of season produce. I'm working on economical ways to control the growing environment (like building a greenhouse), but still be able to use natural sunlight to grow the plants. For me it is all about return on investment (ROI), and what I like to eat.

All good points;
While on the subject of companion gardening & outdoor hydro, does anyone have any suggestions for a DIY system to grow Large Tomatoes & Cucumbers on both sides of a 16 Ft.L. X 7 Ft. H. Trellis (C.R.W.)?
This is how I grow my Big Zacs, Neves Azorian Reds, and Straight Eights in my raised bed soil garden and I think I may have a soil borne disease as leaves begin wilting from the bottom of the plants (old growth) upward, Shortly after mid season.
A runner on each side of the trellis, either NFT or something like the Aeroflow systems would at first seem like logical options, But I just can't envision such a system being able to accommodate the colossally massive root structures that these large indeterminates develop.
Any ideas?
~Ken~

Personally I'm partial to drip systems. Weather you use 2-3-5 gallon buckets, or build a trench type container. Running drip irrigation, and return lines are fairly easy. You'll need the reservoir to be below the containers. For me an in-ground reservoir would fit the bill. A little harder to setup, but will help keep the nutrient solution cool. I have plans to build just such a system to grow melons.

A trench type container, and/or buckets can hold a lot of growing medium though, so finding a economical growing medium is really important to me. For that I'm looking into using pine shavings (and/or possibly even sawdust, although it will compact more). I haven't narrowed down a definite source yet but I have some leads. I think the stuff that's most comonly used is called "Fibralur" but I haven't found a source in the us yet (although it may not be a English term). Here is a outside the US source I found: Fibralur

Here is a source that says they get "clean pine shavings" at Wal-Mart, but doesn't specify what department it's in. Bag culture. After a bit of trying a few different keyword combination, I came up with a few more possible sources. One is from animal feed supply places because they apparently use pine shavings for bedding for horses: Horse bedding.

Another possible source is from playground supply places, here is one that I bookmarked as well: Playground Chips. Note that the first one on the list is 100% organic with no chemicals added, and that 1/2 cubic yard is $19. Then note near the top of the page where they state that one cubic yard weighs 900 lbs. So 1/2 cubic yard would weigh about 450 pounds. They must be figuring the weight of a compressed cubic yard. Even so I have a hard time thinking a solid cubic yard block of wood weighing 900 pounds. It might be a typo and supposed to be 90 pounds, so half that would be 45 pounds. Even so 45 pounds of growing medium for $19 sounds economical to me. Though I would still try to find a local supplier so I didn't need to pay for shipping.

I also read that pine bark was used in at least one study:
Cucumber production in the greenhouse using pine bark as an alternative soil-less media

So I found a source for that also Quality Bark Products.

However I'm a bit skeptical about using pine bark at the moment until I read it all in full because I have also come across another document about pine bark. Chemical Characteristics of Pine Bark. Though this is talking about using pine bark in soil, the part about the "pH of native pine bark is generally 4.5 or lower" has me specifically concerned.

P.S. I still have yet to contact any of these suppliers to make sure there is no chemicals, fungicides etc. in the products. If so that would make unusable for hydroponics. I would also be looking for local suppliers, so I didn't need to pay for shipping.

However it does state:

"nursery crops grow quite well in pinebark media with a pH of 5.0 to 5.5. The difference in optimum pH of the two media is due to the toxic effect of aluminum in mineral soils, whereas pine-bark substrates generally contain little or no aluminum."

HH,
a little perspective. a cubic yard of pine is 200+ gallons.
yellow pine weighs apporximately 35 lbs/ft^3. OF course, with it being shaved there'll be more air, so 900lbs isn't far off.
Other thoughts:
look for local sawmills. They'll probably give you the stuff so they don't have to dispose of it.
In my yard, I have to lime it every years to raise the pH because of the abundance of pine around me. So yeah, It'll lower the pH.

Thanks grizzman,
If a cubic foot of pine weighs 35 pounds, then the math would add up. I have never weighed a block of wood myself. I guess I just imagine it like a couple of 2X4's (3 at most) would probably add up to about a cubic foot, and those don't seem to weigh more than a couple pounds a piece. Perhaps they are talking about wet weight, before it's kiln dried. Anyhow it should be economical to use. I haven't really looked into it yet but I don't think we have many saw mills here in the desert. There's a horse stable near by though, I plan to talk to them and see what they use for their horse bedding. And if it's the pine shavings see if they will sell me some "clean stuff" to try out on a few plants. I have 6, 5 gallon buckets I use for a drip system just waiting to be used for more plants, but I don't have any growing medium to put in them.

If I understand correctly what the "Chemical Characteristics of Pine Bark" document that I posted is saying, is that there is a reaction between pine bark and aluminum found in soil, that significantly lowers the pH ("The difference in optimum pH of the two media is due to the toxic effect of aluminum in mineral soils"). But because the aluminum is not mineral element used in nutrient solution's, therefore not really an issue in hydroponic setups.

Also the document is specifically speaking about pine bark, rather than the pine shavings. I haven't read about any issues with pH of pine "shavings" in hydroponics (yet). Also I haven't yet read the study about using pine bark all the way through yet, but I'm hoping they will cover any issues of pH with that growing medium if there is any. Either way they both have been used successfully in hydroponics, and I know the pine shavings have been used for a long time. So I plan to try both, and if all goes well, also try it later on a large scale to grow about 40 buckets with different varieties of peppers.

Sounds like the beginnings of a good plan. What size trench containers? Would 16 inches deep X 6 inches wide be enough? How about 1/4 inch plywood construction with fish pond liner? For two trench containers 16 feet long I think that would be 24 cubic feet (.89 cubic yards) or 179.5 gallons. It could all be in ground with an in ground reservoir at one end of the trellis just outside the raised bed. Would 15-20 gallons be enough reservoir? A plug at the far end of the drip rail could be used for pumping out the reservoir during change outs. It's all fairly simple. It may seem like a large amount of medium, but it's more in line with what it takes to grow quantity's of cucumbers and X-large beefsteaks in a relatively compact space.
~Ken~

Of course you can make it any size you see fit, and using any materials that are easily available to you. Though I think 6 inches wide will probably do, I would opt a little wider 8-12 inches wide.

Here's how I planed to build mine. First plywood would be stronger, but OSB board would be cheaper and still strong enough. It runs about $7-$8 for a 8x4 sheet around here. I plan the inside diameter to be 12 inch deep, about 12 inch wide, and 8 feet long. Make it as long as you want also, 8 feet is all I need. Though I plan to build 2, set them parallel with each other about 5-6 feet apart, and place a A-frame trellis between the two trenches. You already have your trellis.

To strengthen the box structure, I plan on running 1x2's (they run $0.84 ea here) along the outside for added support. You can use 2x4's but would be about 3-4 times the price, and 1x2's should be enough support. For a trench box that long, I would probably run one horizontal row of 1x2 along the top and bottom of the box. Then periodically place vertical pieces between them.

Here in the desert I need to insulate the roots from the heat, you probably wont want to do this part, especially if you are going to have the trench in the ground. My trench is planed to be on top of the ground. The inside of the box will be lined with probably 2 layers of 1/2 inch (or 1 inch) thick Styrofoam sheet insulation. Glued in with PL300 foamboard adhesive (it's made specifically to glue Styrofoam insulation to wood and construction materials.

Then I plan to line the inside with vinyl sheeting. I don't know if Low's or Home Depot carry it, but ACE hardware just down the street from me does. They have 3 different thickness that run from about $3-$6 a square yard (in one yard widths). For the inside diameter I plan, it should just fit nicely without even overlapping it (except the end pieces. I plan to use 100% silicone to seal the ends and glue down the vinyl sheeting (as well as all corners and edges after the Styrofoam is glued in). Fish pond liner would be just fine, and plenty durable. I don't know how much it runs, but I think I will look into pricing that as well.

For the drain I plan to cut a hole just big enough to run a pvc tube through the wood, and a little smaller than the wood hole in the Styrofoam (for a snug fit). Then glue it to the Styrofoam with the foamboard adhesive. Then run beds of silicone, and screw in a pvc connectors on both sides of the tube and snug it down. Making the lip of the connector on the inside of the box as short as possible (but still durable), so as much water will drain out as possible. I may decide to have more than one of these drains per box. But if one side of the box is raised a little, the water should flow nicely to the side with the drain/s.

Because the heat and sun is so bad here on things. I plan to paint the outside of the box with a roofing material. I forget what it's called, but it's white, thick, durable and flexible. They use it on rooftops for reflecting the suns rays (overall cooling the building). That will also add another layer of insulation for the roots for me (reflecting the heat). But I need to find somewhere where they sell it in one gallon buckets. The 5 gallon buckets are way more than I need, and it's not exactly cheep (a one gallon should run about $10-12). That should protect the wood from moisture if you plan to bury it in the ground as well.

However there is another material for that also, but it's black. I forget what they call that also, but they use it to protect walls that extend underground so they don't absorb moisture (like basement walls, underground stairways etc.). I don't know how much it runs, but you will want to protect the wood from ground moisture if you place it in the ground. And products like Thompson water seal wear off and need to be reapplied regularly.

Once the box is ready, I plan to simply place a section of inexpensive furnace filter screening ($2, I just cut the screening material out of a inexpensive furnace filter) on top of the drain holes. Then I will place a layer of rocks on top of that to about 2 inches deep along the bottom of the trench. This will hold the screening in place and help with drainage all the way through the box. Then just fill with the growing medium and plants, setup the drip system. You should have a very durable planter box that will withstand the weather and you can use year after year. .

I forgot, I would recommend a minimum of 2 1/2 gallons of nutrient solution in the reservoir per plant. Tomato's and cucumbers are large plants, so they will use up a lot of water, especially when they get to be full grown. If at all possible I would try to have a reservoir that can hold more than the minimum (3 to 4 gallons per plant). The more the better, the less fluctuations in nutrient concentrations (EC/TDS/PPM), and pH you will have to deal with. Resulting in healthier plants, and better tasting fruit in the long run.

I'm also considering doing just half the trellis, allowing me to compare plant health and growth rates and reducing initial costs. Also easier to build using 8 X 4 material. This system would also be quite easy to convert to flood & drain should one desire to do so, simply by adding overflow returns and adjusting flow rate and timing.
~Ken~

Sure, making the boxes smaller is very useful. It also makes it easily expandable by just adding duplicate boxes to the setup later. And if you decide to move and/or reconfigure the way you have them laid out for a different space, that will be a lot easier to do with 2 or 3 smaller ones. Rather than being stuck with one long one. You may also want to reuse it later but don't want to use the whole thing, you may even want to make 2 or 3 different systems out of it. You just have many more options with shorter boxes.

And Ya it will be easy to convert to a flood and drain, and/or back to a drip again. My only concern there is that the size of the reservoir will need to be increased quite a bit in order to flood the system, and not run the pump dry. That's what I like specifically about using a drip system for a large setup. But again smaller boxes, not so much of a problem.