Hello aquaponics growers.
This is Jonathan from Melbourne Aquaponics.
In this video, you will learn how many fish you can put in your aquaponic setup.
So that's a question that I receive very often, at least once a week, is how many fish can
I put in my aquaponic setup?
So to determine the quantity of fish you want to put in your aquaponics setup, there are
different factors, and that's what we're going to see into this video.
The first thing is obviously the quantity of fish is going to determine the quantity
of fish food that you're going to put into your aquaponics setup.
Right?
If you got many fish, depending on the species, if they eat a lot, you're going to have to
put a lot of fish food.
If you got just a few fish, you will have to put less fish food to feed them a bit less,
and therefore, all this quantity of fish food that you add into your aquaponics setup is
going to be a quantity of ammonia that is going to be produced, and it's going to be
available first for the bacteria and then for the plants, for the vegetables that you
grow in your aquaponics setup.
So you may think okay, that's perfect.
I want to produce a lot of vegetable so I'm going to put a lot of fish.
All those fish are going to eat a lot of food, and therefore, they're going to produce a
lot of ammonia, which is going to be transformed back into nitrite and nitrate by the bacteria.
So that's good.
The more fish you have and the more at the end, nitrogen you’re going to have into
your water which means the more plant fertilizer you're going to have into your aquaponics
setup.
But obviously, there is a limit here.
The limit is actually the quantity of bacteria that you have into your aquaponics setup.
Obviously, the more bacteria you have, the more quantity of bacteria you have, and the
more those bacteria are going to be able to transform all this fish poo, all this ammonia
into nitrite, which is a food for the plants.
So if you don't have enough bacteria, you will be limited into the number of fish you
have.
Right?
If you have a few bacteria, you can't put too many fish because if you put too many
fish and you don't have the good bacteria in place to transform this ammonia into nitrite
and nitrate the problem is that the ammonia that is going to be produced by the fish is
going to remain into the water, into the aquaponics setup, and that's the same thing for the nitrate.
Right?
So the ammonia and the nitrite that are toxic for the fish, it's very important to remember
that ammonia and nitrite are very toxic.
If you don't have a good population of bacteria, they're going to remain into the tank and
they're going to, at one point, kill your fish.
So it is very important, to make sure that you get enough bacteria to transform all the
waste that your fish are going to produce.
And that's really the limitation in terms of quantity of fish.
To limit on the quantity of fish we can have in your aquaponics setup is not really the
size of the fish tank.
Obviously, you want a fish tank that is enough to offer a good space for your fish.
You want them to be able to swim in good conditions and not being one on top of each other.
But the real limit into your aquaponics setup is the growbed, right, the growbed size.
So if you have a big growbed, and even if you have a fish tank that is quite limited
in size, you will be able to stock your fish tank.
With a high density of fish because you got a big growbed so you got enough bacteria in
your growbed.
I'm talking about the volume of the growbed because that's where the bacteria are living.
Right?
So you understand that the bacteria are living in the growbed.
They’re actually living on the surface of the media.
So here in my hands, I got a few little rocks.
That's where those bacteria are living.
Now, depending on the quality of the media you have, if you have scoria like me, here
we got volcanic rocks, I mean, if you have a media that is very porous and very small,
you're going to be able to hold a lot of bacteria because the media have a high surface area.
So I made a special video about the media so you can find it on my YouTube channel,
and I really recommend you to watch this video in terms of understanding how the media -- what
is the purpose of the media in the aquaponics setup and how to select the best media for
your aquaponics setup.
But today, what I want to say is that if you have a media that is very, very efficient,
or if you have just normal pebbles, the capacity of your system transforming the ammonia into
nitrate is going to be very different.
So the factors that are going to influence the quantity of fish you can have into your
aquaponics setup, are first, the quantity or the volume of the growbed but also the
quality of the media that you have.
And then once you got those two parameters, if you have a very efficient media, I always
recommend to stay below 1 kilo of fish for 50 liters of growbed.
So that's a maximum limit.
So stay way below and you will be comfortable.
If you approach these limits be very careful because that's where you start to have some
problems, when you reach 1 kilo of fish per 50 liters of media growbed.
And here, I'm talking in the best conditions.
Right?
With the best media and a growbed that is working really well with a bell siphon obviously,
so in the best conditions.
So if you have a setup with a media that is not efficient, you have to stay way, way below
these limits.
If you have a setup that is very efficient, you can start to be a bit closer to the limit,
but once you reach a certain quantity of fish, just be careful to make sure that your water
parameters are still good because once you reach the limit of your system, you're going
to see the ammonia and the nitrite that are going to start to raise up slowly, slowly.
So that's where you need to act.
You need to decrease the quantity of fish or the biomass of fish.
So that's really the ratio that I give you today and which is not the aim, which is not
the target at all.
This is the maximum limit where you want to stay well below.
It’s 1 kilo of fish per 50 liters of media when you are in the best conditions.
So that's the maximum quantity of fish you want into your aquaponics setup.
Now, when you start your aquaponics setup, you’re going to start with little fingerlings
and obviously, those fish are going to be very, very small.
So let's take the example of a growbed that is 100 liters; 100 liters is twice 50 liters.
So it means that in the maximum of the capacity of the system it will be 2 kilos of fish.
Now, 2 kilos of fish if in the best conditions.
But now, when you want to put your fish, if you want to grow your fish up to 1 kilo, it
means you will have only 2 fishes.
Right?
You are not going to put when you buy the little fingerlings, you are not going to put
only 2 fingerlings because they wouldn't produce enough nitrogen.
They wouldn't generate enough nitrogen to run the system and to fertilize your plants.
So, at the beginning, you can start with maybe 50 fingerlings and then when they grow you
start to sell some here and there, or you can start to eat some but you always stay
below the maximum limit of 2 kilos of total fish biomass.
Now, if you don't have enough nitrogen that is produced by your fish, it's not really
an issue.
You can always add a bit of fertilizer into your setup such as Seasol or some natural
elements, natural only, to just increase the quantity of nitrite into your setup to feed
your vegetables.
And when the fish grow and they get bigger, then they are going to be able to just fulfil
all the needs of the vegetables, of the plants.
So it's never really a problem of having not enough fish.
It's more a problem of having too many fish and not being able to transform the ammonia
that is generated.
So I hope you learned a few things into this video.
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Don't forget that you can have access to a free guide to build your own aquaponics setup
in the best condition from the description of the video.
It's completely free.
See you in the next one.
Bye-bye.
If you are watching this video on YouTube, you will see that on the description of the
video just below, you will have access to some free gifts.
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A very common problem we have in aquaponics is that we got the leaves of the vegetables
that are turning yellow.
And the reason why is because basically, in aquaponics, we sometimes need to add some
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Otherwise, the vegetables have some deficiencies.
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Have a good crop!