Adding Worm Juice to Aquaponics

One of the more contentious issues surrounding aquaponics is the mineral density of the plants and vegetables that are grown in aquaponics. Critics say how can plants grown in Aquaponics be really nutritionally balanced with all the minerals and vitamins necessary for you if the nitrates they consume basically boil down to just processed fish food pellets? Even though most people that run an aquaponics system also add seaweed fertiliser in the form of Seasol or Maxicrop – you are often left wondering if that is enough to supply your growing plants with all the mineral elements that they require?

Worm Juice added to Aquaponics

Recently working with Geoff Lawton on his “Permaculture Soils” documentary we came across this very issue with industrially grown food based on the three fertiliser ingredients that most farmers use. Nitrogen, Potassium and Phosphorus or NPK as it is commonly known. NPK will grow your plants quite well – but all the other trace elements will be missing.

The question was raised, How do you grow traditionally dense food? Food loaded with all the minerals that the plants naturally require?

This is where Compost Worms come into the equation. Compost worms love aquaponics systems and grow vigorously large and swift moving deep in the grow beds. They tend to also hang around the water inlet pipes near the surface and dive around in the plant roots feeding on fish poop and bacteria, remineralising the fish waste. But if the compost worms are only fed a constant diet of processed fish pellets – where do the extra mineral elements come from to grow dense food?

The solution we are experimenting with is worm juice.

If you haven’t already done so, building a bathtub worm farm to process all your household vegetable scraps is a great idea. Putting a diverse mixture of waste into your farm means that your compost worms can reprocess all the complex number of minerals added to your bathtub and allow it to pass through their gut and collected in your bucket as worm juice.

Worm juice is a light brown liquid that many gardeners use to boost growth in their vegetable gardens. Worm juice is said to provide a wealth of nutrients and minerals with over 60 different elements. It is the enzyme in the worm’s digestive systems that allows all the nutrients and trace elements to become water soluble. Therefore the water soluble nutrients are easily absorbed by the plant roots. Having over 60 mineral elements in your aquaponics grow bed processed naturally for free – is the way to go!

In a standard bathtub system (read our blog how we made our own) you will collect about a litre of worm juice every couple of days.

Worm juice analysis is a complex mix of vital ingredients with an increased number of mineral elements that are easily digested by the plant roots. We’ve been using it regularly by pouring it directly straight into the grow beds undiluted. It cost nothing to produce and is harmless to the fish. In fact we use it as a tonic to really turbo-charge the aquaponics system.

Doing a little research on what is actually inside a litre of worm juice reveals a powerful cocktail of necessary biological ingredients.

Silver Beet grown in Aquaponics

Worm Juice Contents Analysis

  • Healthy bacteria 100,000 CFU/ml
  • Nitrogen(N) 64 mg/L
  • Phosphorus(P) 21 mg/L
  • Potassium(K) 940 mg/L
  • Sulphate 82 mg/L
  • Calcium 62 mg/L
  • Magnesium 150 mg/L
  • Sodium 120 mg/L
  • Copper 276 ug/L
  • Zinc 105 ug/L
  • Manganese .26 mg/L
  • Iron 1.5 mg/L
  • Boron .41 mg/L

Growing good food at home that is nutritionally dense with the full compliment of nutrients and minerals for health and vitality should be number one on everyone’s list. Adding a compost worm farm to your aquaponics system is a smart move and worth looking into.