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.
This is great information!!! Thanks!
I noticed that you regularly use hyrdroton clay balls for grow medium. Would a mixture of vermiculite, perlite and washed sand work. Or even just sand with fish solution and vermicultural techniques. With slight adjustments to the pH could I grow just about any vegetable? Strawberries perhaps. I’d likely need a grow dome too with solar radiator fans installed. Your thoughts on that please? Have you heard of ramial wood chip technology? It uses wood chips as the base for worms to grow. I know it works too without any other ingredients like food scraps. Near fresh cow dung works a treat as well with the wood chip compost. It would be compost tea of course. With maybe the addition of kelp liquid in a diluted form.
Washed sand and fine materials are generally not recommended Chris as it has a tendency to clog the system and people that have attempted to use washed sand end up with anaerobic dead zones in the grow bed with the pH turning nasty as well. Remember the pump is depositing fish waste into the grow bed all the time. Worms can be a partial solution in eliminating fish waste. Some people use charcoal in the growbed with good results. I’m not familiar with ramial wood chip. Three quarter inch gravel (pH neutral) is your best bet for a robust trouble free system. See Murray Hallam discuss gravel bed systems in the video on this link: http://www.ecofilms.com.au/2010/03/21/aquaponics-secrets-trailer/
How long does it take normally for the worm juice to become dead? IE: If I have a worm bin, and I havn’t checked out the juice collection in the bottom for a while, will it still be good?
Thanks for the info, I was wondering what the score was with this.
Is there any danger of overdosing using the undiluted worm juice, either due to high concentrations when first added or as a result of build up over time. Do the plants and fish use up everything in the worm juice or are some components not used leading to increased concentrations?
As worms are useful in the growbed, and the worm juice is useful, is there anyway I can just dump the food scraps straight onto the grow bed? Is there a way of quarantining the growing plants from the waste or stopping the food scraps being washed down into the fish?
Hi Mark, we have used undiluted worm juice poured straight into the grow-bed with no problems at all to the fish in our aquaponics system. The idea of adding worm juice is too add the full compliment of minerals that may not be available to the plants from just feeding the fish pellets. For example, a used banana skin high in potassium is broken down by the worms in a worm farm and released as worm juice which is deposited back into the grow-bed and is taken up by the plants. No rotten substances or contaminants should go into your grow bed, so no, don’t turn your system into a fetid smelly mess. Have a separate worm farm to do that for you. Just harvest the juice and use that.