Hi, I haven't gotten an answer and the question's 2 weeks old so I completely redid my question and hope someone is kind enough to offer advice.
thanks

I don't grow shelling peas, but I do/am grow(ing) sugar snap peas. While I'm not growing them in DWC, I wouldn't think it would be a problem.
For any vining plant, you don't really need anything larger than a 2" net pot since it isn't supporting its own weight. For medium, I like hydroton, but if it is not available, river rock from the hardware store or marbles could both be used.
I would suspect an 18 gallon rez would probably support 15-20 plants. That could probably get you abundant quantity of peas.
I'm of less help with the lighting as I tend to grow outdoors. You could grow the plants in your window then run flourescents in a a vertical orientation right beside the plants.
When first putting the plants into the DWC system, keep the water level just a smidge below the bottom of the net pot so erupting water with sprinkle the medium and provide moisture for the plants. once they're established you'll probably want to keep the water level 3" or so below the pots so the plants can develop some air roots.
That's all I've got at the moment, but please ask any more questions you may have and myself or someone else will surely try to get you an answer.

Grizz do you have lick with the snap peas in the summer? Growing outside do you shade them?

Hi Griz, thanks for weighing in with your great practical pointers. Good idea to consider vertically placed bulbs, too. Do you bother to infect your peas with the N-fixing inoculant bacteria or is that a bad idea for yours since it sounds like it may be a mixed system and that may be too much of a good thing for peas which seem to go light on nutrient ppms anyways (and would you do it for an exclusive pea-system)? I hope when I have some other specific questions to whatever problems crop up you and some of the other experienced members can give a little hand here and there.

For now though let me make sure I follow your suggesting right-- 2" pots sounds great, for that, what sort of spacing are you thinking though? I'd love to pile in all those plants but I would need to have center to center every 4" or so (between each 2" pot hole there would be only 2" from pot edge to next pot edge). What closest approach did you have in mind to get those 15-20?

You probably have a more friendly zone 10 than me or are just extremely talented. Here in 9a you'd have to have an air-conditioned greenhouse to do peas outside now (see image of the Southern Armyworm which finished my 80% shade/20% Sun soil attempt).

thanks!

This post was edited by PupillaCharites on Tue, Jul 2, 13 at 4:00

Well granted they aren't producing very well right now, but they were before the heat started cranking up. I don't shade them in a traditional sense. they get full sun from about 9:00 am until approximately 1:00pm. Then the house blocks them from direct sunlight. This lighting arrangement seems to work well for them and for my tomato plants.
Pupilla;
what are the dimensions of your 18 gallon reservoir? I grow my peas at 8" center, but would tighten that up if I could. (I reuse my troughs and don't want the extra holes) I wouldn't be afraid to plant them at 4" on center if there is ample room for them to grow. In my mind, I envisioned your tub as being one of those long underbed type tubs. If it is something more upright, you can still plant them very close together then seperate the plants from each other as they grow. In fact you could place two, possibly three, plants in a single net pot. I do that with my peas and with tomatoes without any ill effect.
As for the nitrogen fixing stuff, I remember reading about it when I was growing soy. I never bother with anything and have not seen anything wrong with the way the plants produce fruit. Granted, my systems are less than sterile as the season goes on, but I believe its an overblown concern. Don't get me wrong. I have no scientific backing for feeling that way. Just that I've grown peas successfully and soy semi-successfully without it. Semi being that deer consumed my crop before I did.

Griz, looks like about 19" X 15" max 'hole-able' area on the tote lid cover on my shopping list, the Sterilite #1675, which is gross 15 1/8" tall. I'm understanding 4" on center to mean the four inches from center to center I was clunky in explaining.

Exactly about wanting covers for other things, something I've been thinking about too since I want to leave my options open in case peas crash and burn. What if we can find some good plastic sheet to buy, and just cutting a huge rectangle in the cover and attaching with say nylon nut/bolts our own holed lid tops made from the sheet, also because these more re-enforced tote lids seem to have ridges instead of just being flat. Maybe I'm thinking too hard but a reasonable, preferably black sheet which would also help a little to keep the roots and rez dark because most of the light will be from above indoors anyway.

Thanks about the Nitrogen bacteria. I thought a good bug might be better than having nothing and leaving it open for something bad to colonize, plus everyone hocking the inoculant says that even more nutrients are produced/absorbed for the pea. Also, though that too much N is not good for peas (?!!!) and at this point I want to use an economical, basic proportioned commercial hydro fertilizer solution. It's good to know you have satisfactory production without having to make a more complicated nutrient soup.

Everything I'm saying is from inexperience, I tend to sweat over the 'scientific concerns' when working in a vacuum, usually the worries are overblown, not underselling them, but that's why practical info is the only way I'll actually make any progress here and with a little encouragement now, can't wait to get the supplies and post some pictures of how it comes along if anyone is willing to look.

When I replace those less-than-flat lids, I normally use styrofoam insulation. If the span is not too great and the weight not too much, it should work fine.
The best way to gain experience is to jump in. If you don't set you initial expectations too high, then if something goes wrong it won't overly dampen your enthusiasm.
I personally like aluminum foil to keep the rez dark as it also reflects both light and radiant heat. with black plastic your rez will absorb heat from it.
you are correct about 4" on center. with 2" pots you'd have two inches between edges. you might be better off with 8" on center and just double up plants in each pot.

You're right about the black absorbing heat into the rez especially for peas that crave cool temps. I saw the floating version of DWC with styrofoam elsewhere online, but I just wasn't feeling like dealing with shedding from the friction in handling. Another more durable option come to think of it is polystyrene sheet, that stuff is real cheap, and you can get the same material picnic plasticware is made from. a 2' X 2' X 1/32" piece could be about $5., but I don't remember how rigid the cheaper thin pieces are. It's a high impact plastic except for outside probably wouldn't hold up to UV solar light, but for indoors, I think the colorant is titanium dioxide (photosynthectic light reflectance over 95% and weighted average IR reflectance is over 75%) and that would be just fine with me.

Thanks for the nudge. The problem I'm having is wanting to basically order the whole thing at once, somehow as usual I've turned a $35 tub project into overengineered $300 project (meters, nutes, hardware). One stupid mistake, like buying the wrong $50-100 of chemical salts, or the wrong $50 6-pack of tubs would screw me, so that's why I was worried about whether to consider stuff no one sweats like N-bacteria or not.

It's easy for anyone to say, hey just spend the $10 here and $20 there and get yourself a premix nutrient for anouther $20, etc., and chock it up to learning, but reality is I'd end up blowing $50 better put towards good stuff, for one like an air pump than can support more than a small rez or two.

Thanks for all the net pot layout suggestions, at least when I get the tub I'll be confident about making holes based on the available space best seen tub-in-hand. I have to think more about your suggestion on doubling up the plants, sound almost too good to be true, but mulling it over, it's probably a better idea to do that no matter what and then cull as needed...

you won't have to cull any plants. 2" net pots easily hold two plants. Remember vast majority of the roots grow out of the pots into the solution. when they're full grown, the net pots aren't really doing anything other than filling up the holes.
If you're on a budget for starters, don't buy any meters. geta pH test kit for a fishtank at a pet store and don't worry about the EC meter yet. Simply change out the solution every two weeks.(don't forget to put in a drain and elevate it enough to put your catch bucket under) The lights do add some expense, but there isn't much you can do about it if you're forced to grow indoors.
When I mentioned styrofoam, i wasn't suggesting a raft system. Just use the foam to create a flat top to your tub. In this thread the top left photo shows what I'm suggesting. its styrofoam on top of a sterlite tub with everything covered in aluminum foil.

Wish you lived nearby and I could go to an "open house". Those designs are good, pleasantly economical innovations as long as you like working with those materials. The foil over styrofoam will have an order of magnitude better heat insulation than typical lids, and the compact clever fountain aeration is something I was planning on eventually experimenting with in your picture, also very ecomomical and I bet could outperform a bubbler as long as too much momentum isn't flying around. But that's the subject of another thread after I get out of the beginner blues!

Forced indoors, unfortunately yes, and as for the meters, I can't help myself there since I'm the type that believes if you can't measure it you can't improve it and hate flying blind. As you may have guessed, I'm a technical geek and already have a very nice multimeter for my electronics tinkering. I bet it can be rigged to get conductivity just fine. I pretty much assumed there was something special about these EC jobbers but just read that all ppm conversion measurements are BS based on not always manufacturer uniform fudge factors, which suggests these $45 meters are probably lower quality than my Fluke multimeter properly interpreted.

***

On the practical side, you happened to say in passing to be sure about a drain. Actually I had a more clunky design in mind since I really don't want to perforate the bottom of the DWC unless it really is necessary. I was just going to put an opaque siphon hose through (another!) hole in the cover. Is it really that important to get every last drop out during a grow-cycle?

This post was edited by PupillaCharites on Wed, Jul 3, 13 at 13:03

No it's not critical to get every last drop. I'll assume you have an automatic or electrical siphon then. I wouldn't really want to suck up the nutrient.
The issue of multimeters in lieu of EC meters has been discussed here before. As I recall, the concensus was it's not as easy as you'd think to make one.
If you into geeky things (especially those requiring a multimeter) then your best bet would be to simply calculate how much fertilizer you need to add to a given amount of water and then use some other geeky tools (beakers, scales, and graduated cylinders) to measure a known quantity of nutrient. Then simply add water until you've added as much water as you started with nutrient, remove and replace. beyond the initial filling of the rez, the EC gage can only give you a notion of how good the solution is. It can't differentiate between the various elements. It'll tell you how strong it is but not what left in there.
Where (abouts) do you live. It's possible there is someone else who may live nearby and would let you come look at there odd assortment of hydroponic mischief.

Better nutrients than gasoline... but I know what you mean. If you don't want to bother with a pump, to avoid drinking the spent solution all you needs is a 'trap' to connect to your dangling siphon hose if everything is in the one tub. An easy one can be made with glue and two top halves of 500 ml clear plastic water bottles, and it is just as quick as cracking open a drain valve.

I think I follow that you are making the suggestion that I could just prepare the original concentration of nutrients by weighing or pouring standardized nutrient solution concentrations. That was worth a chuckle since I couldn't have imagined it any other way ... but now it is sounding like people use the EC to add without weighing like cooks tossing spices into a broth and testing it until it meets their spec ... that possibility completely went over my head, but I bet it is a common reason to buy an EC meter.

I'm pretty sure something as generic as EC can be managed much more accurately with a good multimeter than the typical HM EC meters I removed from my shopping list. Like you said, EC isn't providing any details about individual ions, all that all you need to do is mix up the right solution once with the scales and graduated cylinders and measure it even using the resistence scale if you are lazy, since ppms are fudged anyway. The only technical issue is to get a standard sized 'cell', I might use a tic-tac case, and firmly attach two flat electrodes facing each other submersed on the bottom, and run two insulated wires out (preferably set in some insulating epoxy, both for electrode tab and especially to keep the wire leads to them dry. So check the 1/resistance and then check it at half strength or whatever your action threshhold is. (same calibration for temperature fwiw) That's the range. Enough on this since you said it's been discussed. I'll post what I did as soon as I'm in business assuming it has convenient application. BTW the open top tic-tac cell like this could be put directly into the rez as a probe to measure since the plastic ought to act as an insulation shield from spurrious readings. Maybe it was a pH measurement that was more complicated because for that you'll likely need a hydrogen selective electrode and interface, neither that a multimeter comes with...

Back to the fun stuff, I was actually thinking of changing 1/3 of the rez every 5 days during heavy demand instead of everything every two weeks and play it by ear as to when a complete change was needed like if yield loss or gunking up. 1/3 every 5 days vs. 100% every 15 seems much better to me as a compromise between dilution and accumulating unused trace nutrients. By the 15th day, only 29.6% of the original spent nute solution wilnot be changed out. That sounds a whole lot better IMO than carrying all the spent nutes till the 15th day.

I'm in northeast FL but so far I don't know anyone nearby doing this. There is a hydro store or two in driving range and one of these days I hope to at least get to one and check it out. But I seriously doubt that they would be so helpful as your pictures from the other thread, which really got me thinking more creatively from the canned stuff all over the web.