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rfeiller
06-04-2011, 12:36 PM
on another thread davidstcldfl referenced the following concerning DO, gpm water flow in their troughs

scrol part way down the page...look for 'Flow rate'...
http://hosted.verticalresponse.com/5273 ... 51f16240b/
Sorry, I didn't seem to 'save' part 2...?

but, the part that interested me was the mentioned the level of nutrients measured at the beginning of the grow bed and after flowing through the grow bed remaining close to the same.

a couple of months ago to try and determine nitrate usuage in a system, i removed the fish and drained a 65 gal aquarium that had been supplying nutrients to a 4' x4' x6" (60gal capacity if filled) contineous flow mat grow bed. I then added water from another aquarium with a nitrate reading of about 80 with a API test kit.

the grow bed has 3 fair size producing tomato plants, 3 fully grown kale plants, about 50 narcissus and daffodil bulbs, 20 glad bulbs, some herbs, a couple of chile plants and some misc. cuttings. after two weeks the nitrate level was reading 20ppm. i realize that i did not factor for concentratin of nitrates due to evaporation, was not able to isolate and measure a growth comparrison to a similiar set up with a contineous flow of 80 ppm of nitrates. but, the plants continued to grow, flower and produce tomatoes and chiles.

however, i expected the nitrates to hit 0 in just a couple of days based on the plants 'purifing' the water. still searching for an equilibrium at what point the level of nutrients can be expected to produce a desireable quantity and quality of plants. a lot of variables i know, but there is a common denominator across the board at some point.

nor, i have i ever seen the nitrates noticeably fluctuate between morning and night. what am i missing here?

urbanfarmer
06-05-2011, 09:07 PM
rfeiller, unfortunately those API test kits have an accuracy of about +-40, meaning that you might test the same water and get 80 on test and 40 or 120 on another test. It's not terribly accurate, which is a problem when doing experiments like that, unfortunately.

As far as the experiment itself, I'm not completely sure I understand what you did. I get that you were trying to take water with a known PPM of nitrate and add it to your system with the plants to test how much nitrate it removed, but I don't know how you did this. Maybe something happened with the pH affecting plant nutrient uptake. Perhaps you caused denitrification to occur and the nitrate turned to nitrite for a while and reverted back when you tested (meaning the plants couldn't absorb it but the nitrate was there when you looked again). I know this seems unlikely (albeit possible), but my point is maybe something else went wrong! Also, the amount of sun, temperature, or root damage from draining the water???

It's just to hard to say rfeiller. If this was a question on the SAT or GMAT I would circle the bubble "not enough information/cannot determine".

Sorry buddy. Maybe with some pictures and even a diagram and a cleaner and more detailed explanation and we could really figure this out! In fact, I would be willing to replicate your experiment!

rfeiller
06-05-2011, 09:45 PM
at one point i use to test products from API. i know how inconsistant some times their regents are. they try to maintain a good quality control but like with the nitrate kit, if the ingredients are not properly mixed (shake bottle 30 seconds, vial 1 min) the accuracy is out the window.
they try to produce a good quality product, tetra and a couple of others produce similiar kits. of course if it is a meter they have to be calibrated constantly for accuracy and you are back to the quality of the regents and how contaminated the solution is. in my home i do not have the controls in place to insure anything but a rough level of accuracy. the best i can do is to be consistent in how i add the regents, how i aggitate the bottles and the vial.
the pH in the aquarium did not change during the test at least noticibly. the temperature in the green house has not been consistent, thanks to the craziest winter since '64-'65.

circling the bubble is a cop out :lol: :lol:

urbanfarmer
06-05-2011, 10:07 PM
circling the bubble is a cop out :lol: :lol:
Lies and shenanigans! :lol:

But in all seriousness, I really like where you are going with this! Just keep in mind +-40 PPM is incredibly inaccurate, even if you have a high precision, you're just getting the same bad data over and over. I think a better way to test, in this case, is start with something like 40 or 80 or 120 PPM of nitrate and record HOW LONG IN DAYS it takes for it to read 0. This would help smooth out the uselessness of the API kit's accuracy for experimental purposes and still give useable data.

I honestly don't believe we need to rely on published scientific research for our aquaponics community. We can perform scientific research ourselves, publish it here, and peer review it with each other (reproduce the results). This is cheap, fun, and gives us tons of information in aquaponics. I'M BEHIND YOU 100% BUDDDY!!! :mrgreen:

rfeiller
06-05-2011, 10:25 PM
try this, to project, say a business plan, a given quantity of product; in aquaponics it's fish and vegetation, you have to have a sound base on which to extrapolate how productive your venture will be. you certainly can't base your projections on well it could be 1 to 1 ratio, or maybe it's a 2 to 1, or a 1-2 ratio or even a 3-1 ratio of grow beds to fish tanks. ah, 40ppm nitrates how about 300ppm nitrates. there are a tremendous number of variants in aquaponics. i have to reduce them down to a predictable base. business, even the business of living requires that a solid basis is created for whatever it is. that is what i am working toward.