Basically, what hex says, and just to add that a 342 calibration is a weak solution and more suited for testing most tap water. But such hair-splitting accuracy won't play a roll in your hydro need as long as you have a way of telling stronger from weaker on any calibration at all. The actual calculations the stick is giving are really a black box if you start splitting hairs and ... conversions get hairy when you deal with summer vs. winter on top of who's calibrating with what and at how strong and at what temperature. Sticking with EC frees you from ever worrying about ppm conversion factors again, except when helping others wade through the mess ppm has caused. So, you can complicate life with ppms or just use the actual signal of the stick gives, which is EC, and never look back, because the ppm is not what is being measured, it's the EC. The only benefit I see to "ppm meters" is that they are cheaper, but not by much. If you wonder how something that has programmed into it an extra level of conversions can be cheaper that the one that simply gives the raw electrical number, it's because mass produced meters are TDS since tap water is usually measured in ppm, and the guy that started making EC meters makes them in smaller runs. In hydro, there's a case to be made for those using a single brand of powdered fertilizer that ppm is easier to relate to gram readings, but to be honest I have never once seen a single post of someone actually using it for that. If you add up the ppms we are actually interested in, like N, P, K, S, Mg, Ca, Fe, etc., the total won't add up to the ppm on your meter, so why bother? Since you already bought TDS, consider it like a speedometer. Mix the ferts new, and check the reading. The reading is your rough speed limit. No one will give you a ticket for going a little bit faster or slower, but major differences and your plants will need to pull over into the shoulder. If you use EC, though as already noted, you will be able to share your results without everyone degenerating into a ppm vs. EC food-fight! EDIT: Let me add, for your purposes, it is not the NaCl calibration with 342 ppm NaCl that will make a squirrel's ass difference. What you want to make sure is that it is compensated for temperature. A 342 ppm calibration would be extremely inconvenient for me if it were only done at 25 C, and not automatically compensating for temperature ("ATC"). Many of the cheap meters do not have ATC, so watch out since even one degree make a difference in solution measurement. for a typical 10 C temp dif, the uncompensated readings of the same brew will be 20% different - and that becomes a problem! This post was edited by PupillaCharites on Fri, Apr 4, 14 at 15:56

Hi again guys, I'm learning quite a lot from all of you. I've gone over the bottle and labels and I'm pretty confused about one thing. The Micro is 5-0-1, the Bloom is 0-5-4, but there are other nutes in some of it that don't make sense to me. I will start with the Bloom (I was wrong before) Available Phosphate (5%) Soluble Potassium (4%) Soluble Magnesium (3%) Soluble Sulfur (5%) This is what it says on the label. What is the purpose of all this Sulfur?? On the Micro there's 5.5% Ca. So, let me get this straight, the Ca ups the pH? Someone told me that C. Annuum don't need much Nitrogen at all, and to get it below 50 if possible. When I do this by using the Micro, I suppose there isn't enough Ca to help with the pH, right? See, I never had this problem before, it was only when the plant got older, which I guess is expected as they're bigger and get more hungry. Here are the readings from my system, both newly calibrated pH and PPM meters 3 days ago, over the last 3 days. pH 5.83 - PPM 472 pH 5.77 - PPM 433 pH 5.61 - PPM 362 Todays reading is.... pH 4.92 - PPM 498 What on earth could be causing a drop in pH and raise in PPM so vigorously in 24 hours? I haven't even touched the system other than check visually quickly. You see, I dare not increase the nutrient amount or they take more damage? So am I starving them or overfeeding them? I have attached a link to some pictures of how bad it looks. They don't look too good :( Link at the bottom of page. Plus the amount of floral abortion (I think that's the name used) is insane. I thought it could be a pollination issue but nothing I do matters, it'll flower, then drop off from the stalk. Hmmm.... Probably every day I see 10 dropped flowers :( Any further help? I'll definitely be changing the solution again today. Just, are you sure putting so much Nitrogen is ok at this stage? Here is a link that might be useful: My sick Chili plants :(

It's been mentioned in a couple other threads, so sorry if you've already read this: PPM is never measured. The only thing measured is EC. Some of us still can't figure out why there seems to be a desire to switch EC to a ratio of ppm, which is essentially pointless. The 500 and 700 scales simply mean you take the EC measurement and multiply by 500 or 700 to come up with a crude approximation of ppm of dissolved solids. That doesn't even mean that those solids are fertilizer (though they likely are). The only number that matters is the EC value. The rest depends on your ability/willingness to follow the directions on a manufacturers label. I don't. I use less than GH recommends, just in the same proportions.

Thanks for the help Cole_Robbie, they died on me, so I will be starting over with a new organic seed batch I bought instead of the seeds I used last time, which were just seeds I collected from some store bought orange and yellow bells I got from a local health food store. I knew about using hydrogen peroxide to clean my hydroton, but I didn't know you could use a weak solution in a spray. Will be cleaning my entire system this week to prevent any issues in the new crop. I forgot to include my light source. My systems are in one of my spare rooms with a big picture window. I have my tomatos in front of the window(West facing) now because they are too large to put under my lights which are 100w SFL's (1750 lumens per bulb) which I have all my peppers growing under. NFT system just has 4 - 2 bulb 40w shop lights that it uses.