Backyard Aquaponics
A place to discuss aquaponics

Ok, so I'm trying to get my head wrapped around the chemistry of Aquaponics. This is my understanding please correct me if I am wrong.

You feed the fish and they produce ammonia and solid waste. The ammonia is broken down by bacteria in the grow beds which produce nitrites and nitrates. Solid waste is filtered out in the growbeds and naturally decomposes. The plants use the nitrites and nitrates. Clean water is returned to the fish tank. You may have to input for PH control. The only other input is fish food.

Correct?

not quite:


You feed the fish and they produce ammonia and solid waste.
yes.

The ammonia is broken down by bacteria in the grow beds which produce nitrites and nitrates.
yes - 2 step process requiring 2 different types of bacteria.
So presence or absence of nitrites are an important middle-step indicator.

Solid waste is filtered out in the growbeds and naturally decomposes.
yes - if solids go direct to bed, you also tend to get some worms etc in the beds which help break down organic matter. Some people do additional pre-GB filtering (not really needed in a simple beginner system)


The plants use the nitrites and nitrates.
nitrates yes. Nitrites not really.
Plant type, pH and levels of other trace elements/minerals can also have a part to play.


Clean water is returned to the fish tank.
not quite, filtered water = yes, but nitrates often end up back in fish tnak, but eventually get used [hopefully] on the frequent GB cycles. If not being used nitrate levels increase in the fish tank, which is not ideal (so having high nitrates >80-100ppm is not really a good thing)

the level of filtering depends on how you have your system set up and how your specific grow bed drain works.

You may have to input for PH control. The only other input is fish food.

you also have to input for trace elements (at low levels), iron and potassium.
Mostly done using organic seaweed extract (Seasol in Australia or equivalent).
In a low stocked system you may have to add a little bit more (ie. Seasol Power feed in Aust).

As Nitrates build we definitely don't want any additional nitrogen being added - so must be careful about what products are used to supplement and when.

Iron is a typical/common deficiency- but depends on system and source water.
and like all good things don't want too much.... Iron depends on pH.

Some balance pH *BUT* should not do too much of this in a young/new system.
Many good systems here run from 6.5-8.2 quite happily.

finally as a rule new AP'ers tend to play with their systems too much.
The most important phase is sitting back and waiting patiently for many weeks.
when you feel the need to play with something grab a beer instead
Get some veg in from week 1 and you will have something to watch.

Thanks Darren.

dlf_perth: A silly question for you. If I start with a million parts and fish tank poo is 5-2-2 on the NPK scale that should give me 5% of the million or 50,000 ppm of N to start with. Why is 80 to 100 bad? 100ppm is almost nothing at all 0.0001% N

Something ain't matching up here! Maybe me. When you all write 80 to 100ppm are you leaving off the k and it should read 80,000 to 100,000 ppm. That I can buy off on. 80k/100kppm might be detrimental to the fish. I don't know yet. And it is probably species driven also.

I don't know if I needed that beer before or after I read an answer to this question. Maybe both times.

Can someone please clear this math up for me?

So the N-P-K are talking about percentages, and the PPM is Parts Per Million, but they are applied to two different things... If the fish poo is 5-2-2 for N-P-K, then 5% of the fish poo should contain N (in some form), 2% P and 2% K (in some form.) However one's fish tank is presumed to not be entirely filled 100% with fish poo.

Darren refers to 80 - 100 ppm Nitrates in the water, your 5% N in fish poo is just in that little bit of fish poo that one might have in the fish tank. I think when you've got 50,000 ppm N in your fish tank it is classified as a bomb, or at the very least a compost bin -- not a fish tank!

--
Sam

Sorry, I forgot to answer this part... Absolutely! Before AND after!



Cheers from Costa Rica!

--
Sam

Sam, You are right I need the beer before and during and after on this one. It is only 7:30 am now so I settled for a coffee. Ok, open eyes first then type would help me.

One thing nice about percentages is that they are constant no matter the amount. So even if you were to remove all the poo and measure it, it would still be 5% N It should all depend on the concentration of poo in the tank. I have a 300 liter tank and to bring the amount of N up to 5% I think I would need 15 liters of it to make the 5%. At this rate the tank should then be at 5%N. the fish would be walking on it. So We would need to take the amount of poo to the amount of water into account. So if I took my 300L tank and divided it by 1 million then times 100, I get 0.03Liters of poo juice N . Then take 0.03/ 300L and it gives me the 0.0001% again of N in the tank at 100ppm. If 1 liter of water is still 1,000 grams then 0.03 is nothing. I have a very sensitive grams scale and even it wont go down that low. It will measure even 1 drop of water.

If I change the 10 to 10,000 it is 3 liters of poo. If I go to 1,000 I get 0.3 liters of poo in the 300 L tank and that feels to be more like what I have. So I am having a problem with the M in PPM. If it is (PPT) pp Thousand it makes sense. 0.3 liters of water is 90 grams (3 OZ) nothing to even talk about. That much ain't going to kill my fish but 10 times that amount would do harm. I still say a factor is out of place here. It just doesn't add up. Maybe after another coffee it will look better. The Math looks like it should be ppt and not ppm. Ok, everyone show me where I screwed up.

If plants on the average need 5%N then there is not enough N in the water to help the plants at the numbers they need. I understand that we are not taking ammonia into consideration yet and the conversion to N. That will take more beers and a lot more coffee.

If average dirt fertilizer is 5-5-5 then I need to find the ratio of it to dirt they suggest.

wow - I don't think I can match that answer Sam..... had to study it in great details to make sure I understood it properly

sorry Deuem, it was not actually even that considered, basically just used the values as they pop at out the Freshwater API Test Kit - which of course only considers *nitrates* (not total nitrogen load). These are just simple levels (basically as elsewhere in forum) that people can relate to.

systems can (and do) run higher but for whatever reason most are happiest and growth is best without too much of anything. It is not about the net load, but simply having sufficient nutrients that the plants just get what they need when they need it. Other issues start to arise when you get too much of things - and it doesn't take long to get chemical imbalance. (always same issue when adding iron, seasol, power feed etc etc)

High nitrates also affect other things like ambient EC, ORP etc (as do all nutrients/minerals).

same old gardening thing. product says add 2 teaspoons so we all put in 2 desert spoons because we want twice as much growth......

-----------------------

Keep in mind that AP is also about the fish....
High nitrates are not good for fish.
First they (along with other chemical imbalance) can affect the taste of food fish.
And there is an onus on us to look after fish in our care and provide them with a reasonable environment..

In natural systems ambient Nitrogen are way lower - unless there is an issue.

10mg/L is (1 mg/L = 1ppm) are typically considered upper safe levels for sustained human water consumption (esp. infants) while 100 mg/l has potential serious health affects (from ingestion). 5 mg/L is considered a basic indicator level for high natural system nitrogen and potential risk of algal blooms (with other things like DO and temp) - 100ppm would be deemed a serious environmental issue. Your argument compares to human waste from septics and waste outfalls... just a drop in the ocean but it causes a lot of issues.

"same old gardening thing. product says add 2 teaspoons so we all put in 2 desert spoons because we want twice as much growth......"

I believe this. The USA gov says that home farmers are most of the reason for high values entering water supplies. Real farmers only use what is needed on a field to save money. Home farmers always think more is BETTER.

I still need to find the ratios for dirt to fertilizer on the 5-5-5 and back calculate it to a GB to see what is going on. Last night I pumped up my Fish water from maybe 5-2-2 to what I think might be 5-5-5 and the seedlings grew about 1/4 inch over night. I just checked and measured a bunch and that is about the average number. Some even pushed out another set of leaves. About 500 seedlings were all just sitting there at the same height for a week. They must of run out of food. All the seedlings are off line of the fish so I can manipulate them as I please.

which basically puts you in the realm of hydroponics - and a completely different scenario.
You will find that their recommendations will be different.

Well the seedlings are off line but I do plan on having what ever is standard for me on line with the fish when the testing is done. Anything that needs a more special or higher level can simply be kept off line. but I am leaning toward Hydroponics, just using the fish water so it is a half baked AP set up so far. I got 20+ fingerlings today so we will have to see what happens with them. At the moment they are in my test 2 FT and kicking the shrimp back to test 1 tank. Test 2 is AP. the shrimp are boxing up a storm to keep the fish away from a free meal. Test 1 is AP with a air water pump. Test 3 is all Hydroponics Half Baked.

There are a lot of smart guys out there who have had this figured out since before I learned to walk, but I'm a fan of the numbers adding up. Sometimes I specialize in that in my day job. Let me lay out a bit better my understanding of how this factors and I'm sure others on this vaunted forum will peer review / squeeze out the slightest error...

First off, definitions so usage is clear...

N-P-K: The percentages by weight in the fertilizer of: Total Nitrogen (Ammoniacal Nitrogen, Urea Nitrogen, Nitrate Nitrogen) - Available Phosphate (P₂O₅) - Soluble Potash (K₂O).

API Freshwater Test Kit - Nitrate test: Measures total nitrate (NO₃) level in parts per million (ppm) which are equivalent to milligrams per liter (mg/L) from 0 - 160 ppm (lifted from test kit instructions). For water (at STP) 1 liter weighs 1 kilo. 1 liter weights 1000 grams as well as 1 million milligrams. So with water (at STP), it is true that "ppm" is the same as "mg/L". Let's also agree that 1 ml of our water-based solutions weights 1 mg like pure water would -- this will make untwisting one's mind much easier...

So tackling the API Nitrate test kit first... if it reads 80 ppm in a 1000L tank, that is 80 ppm = 80 mg/L = 80 mg/L x 1000 L = 80 grams of Nitrates in the tank.

The Miracle Gro Water Soluble Tomato Plant Food 18-18-21 fertilizer contains 18% Total Nitrogen, which they have nicely broken down on their label, as being a combined: 1.4% Ammoniacal Nitrogen, 14% Urea Nitrogen, and 2.6% Nitrate Nitrogen. The label has several different application instructions, but for feeding indoor plants, they say to mix 1/2 teaspoon with 1 gallon of water -- that's 2.4645 ml into 3785.41 ml (assuming US teaspoons here.) So we are now talking about 0.000651 or 0.0651 % of that mix is Miracle Gro Tomato Food and the rest is water.

With straight math we know that 100% is 1,000,000 ppm so 10% is 100,000 ppm and 1% is 10,000 ppm and 0.01% is 100 ppm. So our 0.0651% solution of Miracle Gro Tomato Food is 651 ppm Miracle Gro Tomato Food. Of that 651 ppm we know per GUARANTEED ANALYSIS (says the label) that 18% of that is Total Nitrogen and 2.6% is Nitrate Nitrogen. So 2.6% of 651 ppm is 16.9 ppm. Looks to me like "fish poo" for most is providing higher levels of Nitrates for our tomatos than Miracle Gro Tomato Food.

So in your RO water, if mixing in Miracle Gro Tomato Food per instructions, you'd end up with (let's say) 17 ppm Nitrates before any of the less processed N (Ammoniacl & Urea) is converted.

Does that make sense when bouncing between N-P-K and our more AP common ppm numbers, now?
So can some numbers freak confirm these numbers?



Deuem, I'm a big fan of beer, but I think we've clearly exceeded its capabilities to aid in processing here. I think you should investigate whatever the Chinese equivalent of our Central/South American Yagé (Ayahuasca / Banisteriopsis caapi vine) is. The trained rainforest shamans use it to help people have spiritual revelations regarding their purpose on Earth, the true nature of the Universe as well as deep insight into how to be the best person they possibly can.

Yagé/Ayahuasca
N,N-Dimethyltryptamine
Notes on the Visual Stages of a DMT trip
DMT→ The Inner Path to Other Worlds

While I am a big fan of exploration, if you do really consider something like yagé, please be very, very careful.

Not everyone survives their adventures...

--
Sam

The basics all look ok to me. It is much easier to talk Mg per liter then ppm. It is something one can weigh out. So the mg/l is what I will also use and stop converting everything 5 ways.

Have you found out on the fish poo 5-2-2 if that is in solution or just the poo. On every item I have found with npk values so far it is the raw value, not a solution value, So I will go with the 5-2-2 as being the poo itself. If I were a scientist I would give you the straight value of the poo only. So when it is in the tank it is in solution and we need to figure out that equation like the Miracle Grow one you did.

Lets agree for now that we take the poo out and dry it and mix it to a water solution at the same rates the Miracle Grow people do. Your 2.4645 ml into 3785.41 ml ratio. If the MG turns into 2.6% is Nitrate Nitrogen then the Fish poo should be almost twice as high in N. maybe we should use a different NPK number for the MG 2.6-18-21 for now.

1 Liter = 0.26417205236 Gallons (US) Using 1L = 0.264G So 1,000 liters = 264 gallons

When I bought my empty FT I filled it by hand with an exact 5l container and it is exactly 300 liters and I marked the tank level every 5 liters with a scale. I add and pull off to this scale. The only thing it the tank at this moment is water and 6 gold fish. It is now void of all decorations or gravel, Just glass.

Back to the 1,000 l tank/264G. To raise that much water with MG to those numbers we would need to add 1/2 teaspoon per gal or 132, 1/2 teaspoons.

1/2 Ts = 2.465ml Ok
1 gal = 3.785 Ok, ( I got 3.787 ) keep it at the 5

Using ml when we should be using mg is not the best actual numbers but I would need to actually measure it or do a lot more math and the one nice thing in metric is the liter weight. So lets use ml as the constants for now until we can get or really need the weights in mg. If I were commercial I would use the real numbers. it should be close enough for government work. But if we are actually talking powder vs water we could be several hundreds times off. At some point in time we will need to slide in the right numbers. So I reserve this fact for later and depending on the actuals it may change considerably. The Math wont change, jut the factors will.

132 half Ts x 2.645 ml = 349.14 ml total mg to raise the 1,00 liter tank to 2.6%N FT N @5 / 2.645 = 1.89 times the amount in Ts needed Fish Poo per gallon. Or 132 x 1.89 = 249 1/2 Ts of FP for 1,000 liters 249/1000 *300 for me =74.7 or 184 mg of poo to achieve N5. that is like nothing for the fish to produce. Something still ain't right and I am only drinking coffee Sam. Your turn. I have to go fishing.

One stupid or smart large mountain shrimp last night decided to crawl up the air hose and explore the house not knowing it was his/her doom. it was found 2 meters from the FT and is now Crunchy Gold Fish Food. I had 2 inches of air space he had to crawl over. it is now covered so the rest don't join in. No fish jumped out.

Okay, this is obviously a typo/mistake... 1 ml of water at STP weighs 1 g or 1000 mg. I don't think that mistake affected any of the calculations. It was just a poor off-the-cuff remark.

So how much Miracle Gro Tomato Food 18-18-21 to add to 1000L of RO water to achieve what number? Following those indoor watering instructions, 1/2 tsp per gallon will always result in 16.9 ppm Nitrates. So like you calculated, 1000 L is 264.172 gallons, but 264.172 x 0.5 tsp = 132 tsp. Not 132, 1/2 teaspoons.


That should be 264, 1/2 teaspoons in your calculation, or simply 132 teaspoons.

To double-check the Miracle Gro Tomato Food 18-18-21 math...

Solution is said to be 18% Total Nitrogen, included in that is the Nitrate Nitrogen which is said to be 2.6% of the solution by weight. The application instructions (for indoor watering) say 1/2 teaspoon per gallon of water. One US liquid gallon contains 767.988 US teaspoons, or 1536 half-teaspoons. So our ratio is 1/1536 which is where my 0.000651 number came from. 0.000651, or 0.0651% of the Miracle Gro Tomato Food / Water mixture is Miracle Gro Tomato Food and 99.935% is Water. Following the 1/1536 application ratio to 1000 liters, we get 0.651 liters or 651 ml of Miracle Gro Tomato Food mixed in our 1000 liter tank. 18% of the 651 ml is Total Nitrogen, 2.6% of the 651 ml is Nitrate Nitrogen. So 2.6% of 651 ml is 16.9 ml. Then our number is 16.9 ml of Nitrate Nitrogen in the 1000 liter tank. That is 0.0000169 or 0.00169% is Nitrate Nitrogen. Given that mathematically 1% is 10,000 ppm, then % x 10,000 is ppm. Sanity check on that is 100% = 1,000,000 ppm, right? So checking.... 100 x 10,000 = 1,000,000. Correctomundo!

Okay then, the math works... our 651 ml of Miracle Gro Tomato Food 18-18-21 gives us 0.00169% Nitrate Nitrogen. 0.00169% x 10,000 gives us 16.9 ppm Nitrates. That also jives with... ppm = mg/L = ml/kL. When we knew we had 16.9 ml in 1000 liters (kL) we already had 16.9 ml/kL which is the same as 16.9 ppm.

That passes the smell test as well, at least for me. 16.9 ppm Nitrates seems like a reasonable thing for a brand name fertilizer.

So, Deuem... What I don't know is where did your 5-2-2 fish poo N-P-K number come from? Is that a well known? I just haven't seen it before. Assuming it is reasonable, that just means that the Total Nitrogen is 5% by weight of the fish poo. We don't know how much of that is Nitrate Nitrogen do we?

Are you talking about trying to raise the pure FT water to 2.6% (or 5%) Total Nitrogen? Or 2.6% (or 5%) Nitrate Nitrogen? Given mathematically above that 1% is 10,000 ppm, taking a tank to 2.6% would be 26,000 ppm. I'd expect that to be enough to float a turd.

Please explain the 5-2-2 fish poo business a bit more and also what number are we trying to calculate?

Now you know why they had a recall on these poor Barbies!





Also, long overdue apologies to Mountain Cruiser for hijacking the thread, but you already had all your questions answered quite nicely by the 2nd reply. Everything else has just been us having fun and needing some place to shoot the breeze. Don't be bothered one twit by the fancy math. Darren's tag-line already tells you basically everything there is to know about Aquaponics...

May the fish sh*t and the plants grow.....

And as the fearless one once said, "It only gets hard when people make it hard..." Despite what some of those Aussie AP pervs out there may be thinking, I'm pretty sure he was talking about Aquaponics!

So, I believe I'll double-down my beer money on my earlier calculations...
BTW, I know its a long shot, but anyone doing the Banisteriopsis caapi vine with their AP?

--
Sam