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Have had pretty good luck growing must things except root vegtables. Radishes are okay, but not great. Same with carrots. From growing in soil I know it takes the three main things to be balanced. Nitrogen, Potasium, and pot ash. Plus other things like Iron. In aquaponics, nitorgen usualy isn't an issue, due to what the fish provide in the water. plus I add Iron chelate occasionly. But what are the thoughts on adding potasium, and potash. If I rememeber, if pot ash is down, root vegitables do not do well. Of course then there's the thought is we start adding chemicals, we're not into "true" aquaponics, it's more like hydoponics. All thoughts and oppions welcome

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Thanks Izzy. I'm gonna be so fucked in the A.M. :)

No, Tilapia are wholly inappropriate for these parts. It's Carp for me. I have a buddy who owns a large aquarium shop here, and lets me try "questionable" things out in some of his many tanks. Part of the reason I 'knew' the the chloride particularly at those levels would not harm the fish is that it is used to mitigate nitrite poisoning... http://www-heb.pac.dfo-mpo.gc.ca/congress/1994/tomasso.pdf

I have yet to kill any fish with the KCl at those levels I suggested to Mike. Though if anyone is worried about upsetting Na/K osmotic regulatory mechanisms, honestly it seems like just adding some NaCl in near equal parts would take care of that. 

Other people have had positive experiences salting to 1ppt (NaCl) for general fish health. It is even suggested by some of the "AP gods" I just figured why not replace the Na with K and use a salt that would be plant beneficial as well (yeah, yeah I know the two are somewhat interchangeable in plant/animal biology anyways). 

Again, Izzy many long standing aquapons salt there systems to levels 4 to 6 times higher than those I suggested with no ill effects whatsoever (they actually salt to those levels for the benefit of the fish) Your suggestion that I gave advice that would result in a fish kill seemed silly and ridiculous...Hence the wise cracks and me just blowing you off as a loon. Glad we're past that now...Anyways...

The effluent I've 'discovered' is just what is left over once the phosphates have been extracted and the ammonia has been halved. There is no fuzzy fungi at all since I let the urea hydrolyse into ammonia first and the pH is then very fungal unfriendly. Though I've heard of 'ammonia fungi' in soil, I've not seen any in any of my plethoric storage containers.

http://community.theaquaponicsource.com/group/fish-less-systems/for...

I too believe that the wealth of scientific knowledge compliments such tinkerous endevours, (or at least it should)...with out that body of knowledge each of us would probably be stuck re-inventing the wheel every time we do anything. But, by the same token we should not allow ourselves to become enslaved to by certain conventions that that very same body of knowledge helped to spawn.

What do you buffer up you pH with, or how do you keep up the requisite inorganic carbon source (in the form of some type of carbonates) that bacterial respiration demands if all you ever add to your system is Fe? I'm not asking in the spirit of facetiosness, I'm honestly curious.

Go to sleep guy; just respond tomorrow!

Although it is quite common to use salt for the benefit of many freshwater species, most of the higher concentrations are done for short periods of time in a controlled fashion.  Even if your fish survives, your FCR (food conversion ratio) decreases because the fish has to waste energy regulating the osmotic pressures.  This has obvious economic impacts.  Just because the fish survive doesn't mean there is no ill side effect, short term or long term.  The advice you gave was sound.  I still think that was way too much K, but you can simply reduce the amount added for positive results.  I did not mean to make it sound like I was disputing the reality that chloride ions could be used beneficially, but their benefit is far from ubiquitous.

Yes, plants uptake Na in place of K quite readily.  Did you know that (depending on species) plants can uptake up to 100% of their nutrient requirement as Na instead of K?  Did you also know that most plants take on more succulent characteristics when they are supplemented Na for K?  The trick is that most plants begin to show harmful effects from the Na concentration in solution (not sap) at lower levels.  It's tricky to get them to take up the right quantity without damaging the plant (again, depends on cultured species).  At the first aquaponics conference the horticultural lady from Disney discussed how their AP system used Na instead of K, but they had to monitor it regularly (keeping it below 50 ppm of ion concentration, if memory serves).  She claimed the plants started exhibiting necrotic leaf tissue at higher concentrations.

Interesting pee sludge!  This is an area I would like to learn more about.  Okay, I get the extraction process now for the Struvite/MAP.  It seems like a great idea.  I will read that link later, but a burning question in my mind is, why remove the P when you are trying to grow really big radishes!  Haha  :-)  My first guess would be because the urine contains substantially more P than the N and K required for plant growth thereby accumulating in the system to toxic levels for the fish and possibly other biota?  Anyway, it's nap time, but I will definitely read that link tomorrow.  I once read (maybe still have) NASA research that was a 50 or some odd page document that was a complete chemical analysis of human urine.  I believe it was published in the 1960's or something.  I will look for it later if you are interested.

The biota in my system do all the pH balancing (obviously, since I don't, haha).  It does not gradually change over time.  I allow for stratification of my water column.  This coupled with the low stocking density and slow water flow create the perfect environment.  Large amounts of carbon bioaccumulate in my system.  The carbon comes from the atmosphere.  I pretty much tried to mimic a freshwater lake ecosystem while allowing contingencies for the grow bed.  When I test for nutrients, and that's N, P, K, Ca, and Iron, I can not get a reading above 0.  The only way I even know to add iron is the plants show signs of chlorosis.  Here is what I really think the secret is.  I believe all available plant nutrients are absorbed into the cells of colloidally suspended microorganisms and through symbiotic relationships of some sort the plants extract the nutrients enough to appear perfectly healthy (except the iron deficiencies at times).  ALL I CAN SAY DEFINITIVELY IS, IT @#$ING WORKS!  ;-)

Agreed. But "higher concentrations" being the 3 to 5 ppt range commonly used to treat for fish parasites. Anything below 1ppt seems to be generally accepted as a 'soothing tonic' for our finned little friends.

Since KCl is only 52.5% K by weight 250 to 300ppm KCl is only 130 to 150ppm K. Which is smack in the low-ish middle common range used in soil-less culture. Again, I am not seeing that as excessive in the least for a non-mono cropping recirculating food production system. Quite middle of the road really (59 to 300ppm). Particularly since Mike will be topping up further diluting that rather mediocre concentration. The addition seems like a grand way to 'buy some time' and have his plants do well, while he gets a handle on his pH, and his system, through the passage of time, has a chance to build up a store of such plant essential elements. Most people grow a 'wide' variety of things within the same system. This concentration of K seems not to negatively effect things like leafy greens, while catering to some of the more K hungry crowd. Which is why it was suggested.

Yes, I was aware that some plants can entire replace K with Na, while other plants cannot come even close...and suffer toxicity issues at even 'low' levels. It would seem that there exist both natriphobes as well as natriphiles in the plant kingdom.

The reason for the MAP extraction is in a phrase "2 much N" :)

It is difficult to cater to the needs of many cultivars, particularly flowering/fruiting ones when using just regular 'ol humonia. If you dose to obtain the needed K, the N content at those levels is just way too high for flowering/fruiting...and deleterious effects ensue...This has been the hamstring for pee-ponics, great for leafy greens, not so good for much else.

Also, I like to avoid purchasing mined minerals from industry if I can (in this case P), and drying, hammer crushing, then grinding and sifting bones has gotten old right quick (and I suspect that it rather upsets the missus...though bless her vegan heart she has never really berated me about it). I was also liking to keep things 'self sustainable' and stay within the realm of urine. This aspect appeals to me much more than using fish food harvested from the Oceans the way that it is these days, (or mined). And paying for the plethora of other resources and equipment keeping fish requires. All that additional electricity, air pumps, diffusers, back up power supplies, additional solids/mechanical filtration the time consuming maintenance that some of those filters require etc...But those type of things probably go beyond the scope of what you were asking. Anyways...

Another benefit is storage. It is much easier and takes less space for me to store the MAP. But, since I refuse to discard the K rich effluent it still all takes up some space.

I think I still have that old crooked photocopied NASA PDF study somewhere around here.

That sounds like a really interesting set up you have. Hey, since you are apparently already utilizing much of a freshwater lake ecosystem as a model, have you thought about putting some anoxic zones to good use redoxing iron? It might potentially be a good way to avoid having to add Fe-chelates to the system. Particularly since it seems like a nice balanced Zen ecosystem is what you are after, and you obviously have the intellect and attention to make such Fe redoxing work naturally within your system I would think.

Man, my head swims when I think of all the micro-niche nutrient cycles going on within you system that all those various organisms much be partaking in...

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