Backyard Aquaponics
A place to discuss aquaponics

In hydroponics PPM levels are very important. Is it the same in aquaponics? For example in an NFT hydro system, having the PPM levels too low will slow plant growth. Therefore wouldn't the same be true in aquaponics?

I understand more water makes managing fish easier, however if it's OK I'd like to discuss the best conditions for plants (while still having an environment where fish can grow).

PPM?
parts/million?
If so, of what?
Get ammonia, nitrites, nitrates, pH at the right levels and you should be OK.
(I can never remember the levels, apart from ammonia which should be close as possible to zero, I just check with the colour chart on the test kit)

Sorry, it's Parts Per Million. When mixing hydroponic solution there is a recommended PPM level and a meter can be used to test the levels. Faster growing plants can tolerate higher PPM levels.

Not sure how they compare. My hydro solution has a high Nitrate level. But my smaller AP system has 10 at the most. I think it ends up being different because it is at the level that the plants can take in. In hydro the Na might start high and slowly go down. In AP as long as there is enough being produced at a constant rate.

No mixing required in AP Plachon... except perhaps when adding trace elements to correct deficiencies...

The nutrient water in an AP systems contains all the nutrients (in suspension) for plant growth.

Occassionally, usually related to pH... some trace element deficiencies occur, particularly iron and potassium... (several threads and many posts concerning both... try a "search")

Most of the trace elements are contained in the fish feed... uneaten feed, faeces and excretion of ammonia, which gets converted to nitrates for plant uptake...

Provide all that's required.... put away your truncheon, forget about EC readings... pH is the primary factor in nutrient uptake in AP, just as it is in hydro...

Cycle your system, test when needed, feed your fish correctly... and go and sit down and enjoy...

And while on the subject, before anyone raises it....

An AP system is constantly circulating nutrients... and is constantly being replenished with nutrients...

The plants uptake what they require over time.... all of them... not just the first ones in line, starving the rest... ...

The only time you see indications of lack of nutrients is either signs of minor deficiencies or zero nitrate readings ....

Due to heavy vegetative growth, dealth with by either feeding more or adding more fish... or by adding small amounts of specific trace elements....

It's that easy...

Thanks Rupert. This discussion actually carried over from another thread we're ppl were wondering if having a larger sump and therefore more water, would dilute the nutrient levels leading to slower growth.

Diluted nutrient levels in hydroponics would lead to slower growth, so why isn't it the same in aquaponics?

Nitrates in AP are different to synthetic nutrients. There does not need a be a why and wherefore, and quite frankly I dont care - it just works.

And once again for the benefit of anyone who didnt see the replies in the other thread.

A bigger sump does not equal less nutrients. Your plants will take up the same amount of nutrients, regardless of whether the sump is 200 litre or 50000 litre. Your fish will produce the same amount of nutrients regardless of whether the sump is 200 litre or 50000 litre.

Sure, it will take longer to reach the same nutrient level, but the same level will be reached. Ammonia and nitrate off gassing will increase in a bigger sumps, but not enough to dramatically skew the results.

Sorry to be a pain, but I'm very interested in the 'why and wherefore'. A better understanding of this and the differences between aquaponics and hydroponics has a lot of benefit.

Increasing the amount of water won't decrease the amount of nutrients, but surely it would lessen the concentration?

Unlike hyrdoponics, aquaponics seems to be about achieving a balance and letting nature do the rest. I'm just trying to figure out how different water to fish/plant ratios affect that balance.

It seems that fish to plant ratios are very important, but the water isn't so important, as long as it's clean enough to support the fish.

The plants dont care what the nitrate level is, as long as there is some. The fish do care about how much water the have, and the resulting quality.

If you have a nitrate reading of more than 0, it means that you are creating more nutrients than your plants require. If you have a nitrate reading of 0, you are using more nutrients than you are producing. As long as you have a nitrate reading at all, it doesnt matter if its 1 or 50 - your plants are growing as fast as you will.

Once again, dont try to cut corners on fish tank volume, trying to supposedly optimize this and that. If your water parameters end up bad (very easy in a highly stocked, low water volume system) your plants wont give a toss - but your fish will die. Forget about hydro - it is totally different.

Or just ignore me

I won't ignore you mate, your info is helpful. I have a small dam on a property and would one day like to set it up for aquaponics. The water volume would be huge, so I'm trying to work out if it's feasible.

People use huge swimming pools, that are relatively lightly stocked - just match the growbed volume to the fish, water volume does not seem to be the issue.

Dufflight, master of big pools - what do you reckon?

Keep those thoughts uppermost in your mind Plachon... will serve you well, even if you don't have a complete undertsanding of the mechanics...

And that's the thing about AP... there's a degree of "art" rather than "science" involved... as every persons system, climate and fish species is different...

The key is as you say ... "about achieving a balance and letting nature do the rest."...

My pool has a Na reading of 10 and my small system had a reading of 10 and is now 0. The larger system takes a longer time for the numbers to change and a lot of the Am might get losted(gassed off). The GB area I will have to set up is going to be huge and the amount of fish will have to be high. Only time will tell if such a large amount of water has any advantages other than flexibility in the readings. It takes a lot of work to get the pool to spike but the smaller one is very easy and fatal.

Rupert, we may have our differences of opinion on technical matters, but your knowledge on plants and nutrients and of fish by far exceeds mine
thanks for all the things you have let me learn

If Rupert allows me, I would like to highlight a sentence in his explanation:

that might explain:
in a balanced AP setup the plants have constant access to a lot of water with all the nutrients in them from which they can take what they need for growth whenever they need it
In hydroponics the amount of water involved is much, much less
so to provide the necessary amount of nutrients the concentration must obviously be higher

Am I right in concluding that the risk of over-feeding your plants (if that is possible?) is much higher in hydroponics than in aquaponics?

it is my opinion that AP is much more tolerant and self regulating than Hydroponics

PPM stands for parts pro million. Multiply that by the water volume fed to the plants gives you the total amount of nutrients.
maybe for AP we should "invent" an new term like TNS total nutrients in system

TMHO as long as TNS in an AP system equals (water volume fed to the plants * PPM of nutrients) in hydroponics, the plants would get the same amount of nutrients in both systems

I too am very interested in the 'why and wherefore':
better understanding allows for better control


is undoubtedly true, Rupert
but there is also a great deal of science and technics and technique involved in Art
it is not all about talent and intuition
understanding what is happening and what you are doing makes you a better artist


this brings in a time factor: if the nutrients are too diluted (which probably doesn't occur in a stabilized AP system with enough fish), you might not be able to pump enough water in a day to your plants to feed them sufficiently

frank

greetings

Frank


Frank

Plachon, when you posted the question originally I puzzled over it for a little while. It does actually make sense eventually (at least it does for me)

Suppose there's a fixed amount of nitrate available from the nitrfication process (ie fish are producing a constant amount of poo). There's a fixed amount of water being added to the growbeds each day. The plants use this water. If the nutrient levels are staying constant, then the plants are using the same amount as the fish are producing. As long as this equilibrium is maintained, it doesn't matter to the plants how big the fish tank is.
The number of fish, plants and flowrate through the beds will determine the final ppm.

Changing the tank size will change the total mass of nitrate (eg 10kl tank @ 10ppm = 100g vs 1kl tank @ 10ppm = 10g) but the ppm and the flow of nutrients to the plants would stay the same.
Levels in a larger tank will take longer to establish when cycling up, but once established will be more stable, which is good for the fish AND the plants.

It's a pretty complex thing to think about

Hygicell, please try to think this through and it eventually 'clicks' into place - ignoring offgassing etc, a big tank does not cause diluted water once equilibrium is reached. The plants determine the concentration by finding their own balance.
One goldfish in a 10kl tank, feeding one tomato plant with have the same ppm as one goldfish in a bucket feeding one tomato plant if the flowrate is the same.
Increasing pumping rate will reduce the equilibrium concentration.

As an aside, is it possible that fish poo solids carry nutes into the beds without ever being dissolved in the fish tank water?