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Question from DQuincey Hjornevik:

OK, I get to not add the fish right away. No fish no ammonia so you add fish food. What amounts of fish food or ammonia for what size systems? No bacteria no Nitrites and so no Nitrates. Thanks for warning about these issues. More please.

Response:

Thanks DQuincey, that is a very interesting question. The general advice is to add a handful of fish food but you are raising a good point here. This quantity of fish food is linked to the quantity of bacteria we will have to develop so I will do my best to give you a bit of technical information:

The quantity of fish food to distribute in your fish tank will be dependent on the temperature (summer, winter), the volume of your growbed and the quality of your media. All those values will have a huge impact on the general biomass of bacteria able to be developed in your system as well as their growth rate and their nitrogen needs. Because we are cycling the system without fish we don’t really mind to give too much food to our bacteria, it will obviously create a large peak of ammonia and later nitrite in our setup but it will slowly decrease as the biomass of bacteria will grow. If you put way too much fish food than needed the bacteria will take a bit longer to transform the whole Ammonia and Nitrite and therefore after a month of cycling you could still have some toxic nitrogen in your water.

I see 2 ways to approach this exercise:

The first option is to develop the maximum biomass of bacteria that the system can handle. Example you have a 1000 litres setup with a growbed of 250 litres filled with very efficient media (small size Scoria/clay balls/other very porous media). As a rule of thumb I know that this kind of media can accept up to 20g of food per 50 litres of media per day (variable depending on temperature) so the whole system could take up to 100g of fish food per day. We know that the bacteria biomass growth is exponential (certain populations of bacteria can double every 20 minutes) so the first days of cycling the bacteria biomass will be extremely low and in the last days the population will be at the maximum. To develop the maximum bacteria population we can simply distribute the equivalent of 5 days of fish food so 500g.

From my perspective this option is not the best as it develops the maximum population of bacteria that the system can handle but it’s never useful as we generally start from fingerlings fish (very small fish). In result it waste too much fish food and if the estimation here is slightly wrong or if the water temperature is too low, the nitrite will take a lot of time to come back to 0 and the cycling process will take more time than necessary.

The second option is to have for aim to develop at least the quantity of bacteria necessary to handle the biomass of fish that you will introduce in your setup just after cycling. The rule to follow is to distribute the equivalent quantity of 5 days of fish feeding in your system. For that imagine the biomass of fish you will have when starting your setup. Let’s take the example a 1000 litres setup that starts with 50 fingerlings of 3g each. The total fish biomass will be 150g. Let’s imagine its summer, the feeding ratio will be around 6% so the total feeding needs will be 9g per day. In 5 days you will approximately need 45g of fish food.

You see here that using those 2 methods, any quantity of fish food between 45g to 500g will correctly do the job. Note that in the worst case scenario if you put too much fish food you will have to wait a bit longer for your toxic parameters to come back to normal, if you put too little quantity of fish food you may experience very little peak of ammonia and nitrite when you introduce your fish but it will probably not be significant as the bacteria population will very quickly adapt to your new fingerlings population. The bottom line is that I personally think that a little handful of fish food will easily do the job for most backyard aquaponics size setup and I don’t think very necessary to bother people with those painful calculations based on estimations anyway. 

As you know, in all gardens we find bugs that are eating the crop. In classic agriculture the farmers are using pesticides to kill the pest and by doing so they kill the majority of living creatures. In aquaponics we will not follow this principle for 2 reasons:

  • First we can’t use pesticides in our growbeds as the chemicals would contaminate the fish and probably kill the bacteria.
  • Secondly in a monoculture (classic agriculture) there is no biodiversity and once a pest is present it spreads very rapidly on the whole crop. The aim of aquaponics is to produce in a sustainable way and to use the natural cycles. In nature all populations are balanced, each population is regulated by a predator. This is this specific particularity that we use. Working with a variety of vegetable species allow a wide biodiversity of insects and therefore each pest has got a predator present into the ecosystem. Biodiversity is the key to preserve your crop from predators and I highly recommend to have a multitude of vegetable species in your growbed.

2 easy tricks in order to protect tomatoes and other red fruits in your aquaponics garden. I can’t promess you that it will work everywhere but it worth the try!

3 facts about the bell siphon (in aquaponics)

The Bell siphon is a key component of the aquaponics system. In this video we will see:
1: The purpose of a bell siphon,
2: What it is composed of
3: How it works
A well designed growbed aquaponics system equipped with an efficient bell siphon request a very small water pump and is therefore very sustainable.

 

 

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