Backyard Aquaponics
A place to discuss aquaponics

Hi there!
I hope this isn't inappropriate for a first posting, but it's some kind of an emergency

Firstly a short introduction of my person anyway:
I'm located in Southeast Asia (I am not native english speaker/writer btw) and my background is hydroponics related (not uncommon here I guess), more specifically design of setups and development of nutrients. I'm some sort of independent researcher who focusses on alternative crops and culture methods. Obviously I've been interested in Aquaponics for a wile already - but haven't settled for a first setup because of a few reasons. Among them is the fact that I am not a real fish consumer and I always thought that fish culture is tricky for unexperienced people. I am anyway amazed what you guys grow with the "second- or third generation" of Aquaponics. And I'll give it a small scale shot sooner or later! Eventually I'd like also to participate in some other discussions related to some of my interest, I've been enumerating.

But besides my background, here's why I actually call in rather bluntly:
There are still some antagonists of Aquaponics around, (as some of you may have noticed as well) who are sticking to wired prejudices and (intentionally or not) spreading distorted info and the wrong word - or even arguing with people that are getting too enthusiastic about Aquaponics. Worst of all, they do their little "spare time campaigns" in places where most members haven't got enough knowledge and fall for old school prejudices and fallacies. I'm trying here to narrate about it in a satiric yet neutral way - but actually look at that situation with one smiling- and one crying eye.

Actually I should directly invite those people to this place and see how long their claims could resist a different logic, based on experts' knowledge. But I am afraid they will not follow my invitation for a good reason...And this way I'll take the opportunity to complement my knowledge and understanding of the topic.

Anyway, here are the sad facts:
Antagonist X (who apparently has no actual experience with Aquaponics) simply claims that it isn't possible to grow tomatoes in aquaponics, because "most fish" (except Tilapia and another specie) can't survive in higher concentration as 50 ppm of Nitrogen. The max of N-concentration for later species could eventually accommodate to, would be a max of 100 ppm. The argumentation then continues that 100 ppm of N-concentration wouldn't be enough to "successfully" grow toms ("backed-up" by the claimer's own experiences in Hydro). Actually not a backup, but more what I tend to call a selective observation that isn't backed-up at all.

For my understanding, turning the argument on it's head here, simply doesn't work. First of all in my own experience, 100 ppm of N isn't really the optimum (compared to what is commonly used in hydroponic nutrients), but still sufficient to grow tomatoes. But most importantly, the N-concentration in the growing beds, actually in the root zone of plants isn't the same as the one in the fish tank, or is it? And if I got it right, aquaponics is more closely related to soil culture, where N-concentrations around 100 ppm (or even less) are actually quite common and sufficient!?

Yet, I need backup from some experts here to nail it, as I wouldn't like to loose the argument and let people propagate wrong claims because of an early guess that turns out in a stupid cop out from my side...

I've done some searching and googling, but I couldn't find actual data on PPM concentrations of elements (limits, recommendations, tolerances, etc) in growing beds compared to fish tank.

And one more thing here: I was anyway thinking that N-levels aren't the actual issue in supplying enough nutrients to tomato or other "high feeders", but the rather poor content of Potassium in "fish poop"... I've noticed, that some strategies even complement potassium with "external" components ( commonly used in hydroponic nutrients) as potassium sulphate. What about that point, - is enough potassium supply still an issue with aquaponics, or can this be solved otherwise as supplementing it by mineral (some may call them chemical, others chemically processed) components? Are there so called organic means, as in natural minerals, which actually are inorganic btw... well that's quite another story

Hope I got the right tone and that it fits in here somehow...well you never know!
Thanks a bunch!

and Cheers
Lucas

Something to remember with AP. The nutrients are being continually generated. Unlike a system where you add a high concentration at intervals ranging from days to weeks in AP the nutrients are fairly constant. The result is that you have a lower value all the time rather than one oscillating from high to low. I wouldn’t be suppressed that if you averaged it out that AP while certainly being lower wasn’t as far off as people might think.

Hi Lucas and welcome.....

I only just skim red your post so please forgive if I have missed something......but Tomatoes are nitrate suckers....and can never get enough nitrates for their survival....

And we add pot ash for better flowering......and better fruit set........generally my system....like most run on no nitrates, but the plants still grow, it's just they take it up so fast, nothing ever registers...

Here are a few pics of my crop of tomatoes last year.....so go figure

Another point I guess. Yes Hydroponics will probably give you a bit better yield than AP because you can push things to the boundary and only have to worry about the plants. AP however gives you a secondary crop which should more than make up for a slightly lower yield.

Sorry but I strongly disagree....I have pushed the nitrite and nitrate boundries...and from a few experiments, with urea....it can be done....as long as the collony of bacteria can keep up with high levels of ammonia, and will multiply ...of course in excellent parameters of pH , and temp. Accelerated grow can be achieved, ad it won't harm the fish, if introduced at a regulated slow pace

Thanks for the interest and the quick replies from all.


Never mind, I've even not noticed...



True for soil culture and probably AP (I've learned the abrev. today) but in hydroponics, too high N-levels can even be an issue - as too vigorous growth may lead to blossom drop and preventing good crop setting. Just pointing out the difference...

The photos speak literary for them selves, - but actually I was looking for some data....
I understand that you guys see it from a pragmatical point of view - I probably would too if I was in your situation. I don't want to sound obstinate either and focus to much on the argumentation I have to perform... But look, just as a reminder - that guy tried to (erroneously) impressing people with data as in 100 ppm of nitrogen . So I have to strike back with the same currency to be fully credible. That's why I am still looking forward for some data I can use. Or perhaps, I simply forget about the antagonists and that argument and chat with you guys instead...

Thanks again...
Lucas

mmmmn scientific data....I am sure there are a few that would of done the maths on it all.....but i am only a back yard hobbiest...and use my ears, eyes and nose..and common scence ....sure there will be a few more people that will drop by your thread with statistics and experience.......anyway....good luck, make a system and just have a go

You Know Lucas..the best data, is your own system giving you experience.......yourself pushing the parameters......not just a big bunch of numbers other people can supply you with....
1 = it doesn't really corrospond to anything, and until you have giving it a go....the ups and down's don't balance out, because it is a data sheet with a big mob of number's , not a grown product just my thoughts anyway

Yes Jessy, probably true in most cases and in general practice. And I basically agree that for most people a bunch of numbers and scientific data will not do the trick at all.

But in this case it's a bit different:

1. As I pointed out earlier, the argument I was talking about was based on a claim with specific data in the first place. Hence I could make very good use of data that proves that claim as being wrong. I simply would have an edge then.

2. I am in fact half handy man and half scientist. As a gardner and "hill billy" (ex fisherman as well) I use to do as you said earlier: I use my senses, my instinct and my observation skills - and mostly learn by doing. But I am a developer of nutrient formulas as well and as a simple matter of this fact, I often deal with calculus and data (because that is how it has to be done). I don't want to brag around, but I am able to conclude many things from data too (yet without doing any advanced rocket science so far). In fact both, left and right cerebral hemispheres are alternatively challenged by my work - and sometimes the even seem to be up to the task .

I may add the following simplification to my previous questions, in order to hopefully make things easier for future readers of this thread:

1. What is the actual tolerance (maximum) of Nitrogen in a fish tank with Tilapia (and/or other species)- please specify in ppm?

2. Obviously the actual concentration of Nitrogen in the fish tank vs. the actually (and continuously ) available Nitrogen in the growing bed is different. How much would that approximatively be (1/? or percent)?

3. Is there any data about Nitrogen concentration in the growing area that one can reach with AP, without compromising the fish?

That would be all, thanks so far

I still think people are missing something. You do NOT need large amounts of available nitrogen in the water. In fact AP is based on the principle of balance, that the plants should use the nitrogen as fast as the fish/bacteria can generate it. This is a perfectly balanced system. You should only get high levels if the fish are producing more than the plans can use. Ok I am not chemist but that is the way I read it. There probably are variations based on the amount of light and when you feed the fish but ideally it should be in = out.

So if you use plants that demand a lot of nitrogen then you can beef up your bacteria production (ie very large bio filters) and increase your stocking density and feed levels.

Actually that makes me think. What are the high nitrogen user plants? By using the right plants we should be able to optimise the fish levels.

One thing that I can see is a valid potential problem with AP. It is a delicate system. Something goes wrong and the fish die, the fish die and the plants die. Alternatively if the plants die then the fish die.

With Hydroponics you are using a controlled external source of nutrients so only have to worry about plant diseases etc.

Not that I am defending the hydroponics system. There is a reason why you cannot call hydroponic grown plans in Australia “organic”. I certainly would not want to drink the stuff they use in hydroponics.

Fish die from bad water parameters... usually either depleted oxygen levels ... or under-filtration...

Indeed... under-filtration is often the reason for depleted oxygen levels... as the biological load exceeds the oxygen requirement of both the fish and the bio-filtration processes...

Doubling the stocking density, while halving the filtration ratio.... as seems to be becoming the norm these days..... will kill your fish....

And the number of fish kills over the past year just clearly shows the stupidity of this approach...

A well designed, balanced aquaponic system... will not kill your fish.... or stress them such that they become suseptible to opportunistic pathogen attack.... and sick/dead...

Depletion of fish stock... through complete harvest or mortalities...

Wont kill your plants... it may slow their growth if you leave the system un-stocked for a month...

But just as with "fishless cycling".... plants can be kept alive and growing by the addition of seasol...

As to the question of "nitrate" toxicity to fish.... a question that repeatedly comes up...

Despite asking this question many times at my NatFish aquaculture course... and reviewing all the data I could find...

The answer is always the same.... nitrates are not a problem to fish under levels of 500ppm... with most happily coping with levels exceeding 1000ppm...

The latest research I found on the question... suggested that "Blue Gill" were the most suspeptible fish species... at 400ppm...

And the data I've seen suggests... as does the evidence of hugely stocked Tilapia RAS systems.... that Tilapia are in fact capable of exceeding 1000ppm....

I would be interested in reviewing the "link" that suggests otherwise...


As suggested previously... nitrates are always being produced within an aquaponics system... and are available for plant uptake as required....


And many, many systems... particularly the older mature systems... constantly return test valuse of ammonia=0, nitrite=0, nitrate=0....

Are grow profusely...

Other systems have seen readings of nitrates at levels of 100+... usually because the growbeds are barren, or recently replanted...

I suggest that your friend(s) come and read... and look at the many systems on the forum...

And then try it for themselves.... and see if their beliefs still stand after a year...