Aquaponics System FAQ's

Aquaponics Frequently Asked Questions

What is an Aquaponics system and how does it work?

An aquaponics system is a combination of Aquaculture & Hydroponics. The water from the fish tank is circulated through a grow bed in which plants are grown. Nitrifying bacteria convert fish wastes into plant-available nutrients. The plants use these nutrients as their main nutrient supply. The fish benefit from this process also, as the water is filtered by the plants, giving the fish clean water to live in. With an aquaponics system, both the fish and the plants not only grow well, they flourish.

What are the benefits of using an aquaponics system to grow food?

  • Reduced water use
  • Reduced chemical use
  • Reduces pesticide use when set up in a greenhouse
  • Reduces erosion by eliminating the need to plough the soil
  • Reduced running costs compared to a conventional horticultural farm
  • Stops backbreaking work of digging the soil and weeding for the home gardener
  • Can produce fish and plants for the family/grower all year round, using a greenhouse
  • Compared to conventional Hydroponic growers, Aquaponics does not need to use chemical nutrients for the plants, as the fish waste provides these nutrients to the plants. This eliminates the pollution of waterways, which is usually used to dispose of the eliminated chemical water.
  • Compared to conventional Aquaculture growers, an aquaponics system does not have a build-up of wastes in the system that causes the water to become toxic due to the nitrites. An aquaponics system utilises this waste, with the bacteria in the grow beds converting the nitrites into nitrates, which the plants then consume as their main nutrient source.

What are the different types of aquaponics systems?

There are 3 main types of aquaponics systems:

  • Media Based
  • Deep Flow / Raft
  • NFT (Nutrient Film Technique)

Media Based is the most commonly used aquaponics system in the backyard, Deep Flow / Raft design is used mainly in commercial situations, and NFT is the least used design in both backyards and commercial systems.A Media Based aquaponics system uses gravel or expanded clay medium located in grow beds where plants are grown direct where they are sown. The grow beds are usually flooded and drained periodically, allowing water to circulate through the system on a regular basis.A Deep Flow / Raft aquaponics system is constructed with long channels which hold water at a depth of around 30-40cm depth, with boards that float on top of the water. Boards can be made from styrofoam, plastics, or anything else that you can get to float. Holes are made into the boards, and net pots are fitted. Plants are either sown directly into the net pots, or transplanted from other growing area. The plants grow with their roots always immersed in the long channel of water below the boards.

How many fish can I keep in my aquaponics system?

It depends on various factors like the size of the tank and/or filter, and the amount of plants. Generally we recommend 1kg of fish to 80L of water for a non-commercial aquaponics system.

How long does it take for fish to grow to harvest size?

About 2-3 years depending on the feeding rate, water temperature, species of the fish and size of the tank, among other factors. The best results we have heard of in Brisbane are 600g Jade perch in 12 months.

Do I need to add nutrients to an aquaponics system?

Not usually, however, if the plants exhibit signs of deficiency, you might need to. Things that you might need to add can assist with enzymes in the grow bed, pH adjustment or assist with nutrients for plants. For example, iron chelate is commonly added to an aquaponics system but often mismanaged. Iron chelate a powdered form of iron that is cheap to source, however doesn't contain all of the iron types necessary for plants. At our shop we recommend DTPA Iron Chelate to boost the iron content the system and stay in solution for the longest time. There's also GT Liquid Iron, originally a hydroponic additive, to make an immediate difference as it is readily absorbable.

How often do filters need to be serviced in an aquaponics system?

The pump filter will need to be cleaned once every 2 to 4 weeks depending on the quantity of fish.

Growbed and fish holding tank made from an IBC