Fish Feed Rate for Vegetable Growth

In hydroponics, the rate of nutrient feed required to grow plants is easily checked with a digital EC (electrical conductivity) pen. However unlike hydroponics, the nutrients in aquaponic systems are organically bound and cannot be checked the same way. The nutrient feed rate, or "fish feed rate", for plants in aquaponics is a little more involved.

Balancing the Aquaponic System

An aquaponic system requires a balance between the fish and the vegetables, and just as importantly it requires a bio filter (nitrifying bacteria) to support both units.\n\nWithout enough plants, the nutrient levels (nitrates) rise and can become poisonous for the fish.

Without enough fish, the nutrients are insufficient for the plants which reduces yields and leads to deficiencies.

A successful system has the right amount of fish for the plants being grown, in other words, the ratio of fish feed to plant nutrient demand is being met. In addition to this, the bio filtration capacity supports the nutrient conversion required.

Balancing Considerations

fish feed rate

When balancing the system, the main things to consider are:\n

  • The type of plants you want to grow?
    • Nutrient hungry tomatoes and other fruiting vegetables, or less hungry leafy greens?
  • How many plants do you want to grow?
    • Would you like to be as self-sufficient as possible, or just target those vegetables you need on a regular basis?
  • Type of fish?
    • Barramundi can eat much more compared to native Australian perch. A larger growing area and / or nutrient hungry plants can solve this.
  • Method of filtration?
    • Are you using a single grow bed as your filter, a pond filtration system, or even a sequence of biological and mechanical filters? The more filtration the better, as this supports the conversion of feed to nutrient for the plants.

Aquaponic Fish Feed Rate

As a general guide, the fish feed rate for vegetables is:

  • Leafy Greens: 40-50 grams of feed per square metre of grow area, per day.
  • Fruiting vegetables: 50 - 80 grams of feed per square metre of grow area, per day.

In addition, it is likely some iron and potassium supplements will be required depending on the type of your fish feed.

Guide to fish feed size

Aim for fish pellets to suit the fish as follows:

4mm Pellets

Fish weight 175 - 350g

Fish Length 18 - 28cm

6mm Pellets

Fish weight greater than 350g

Fish Length greater than 28cm