As part of my rfeiller’s outdoor garden construction posted in the Aquaponics Magazine website, I had set up 29 five gallon plastic buckets that mostly contained latex paint in their former life. We installed one barbed bulkhead fitting through the bottom of each bucket to drain into a collector to dump into the 600 gallon Biopond. In these buckets layers of worm bedding, compost, manure, veggie scraps, etc were placed. Just above the bedding some bed run worms, castings and partially digested worm bedding was placed. In each bucket was placed one plant (compost volunteers don’t count).
The intent was for the nutrient runoff to be channeled into the 600 gallon Biopond as additional nutrients to supplement those produced by the fish. In spite of having worm boxes and utilizing the liquid runoff to fertilize plants in pots and in the yard for many years, I have learned a hard lesson. The liquid that drains out of a worm bin is NOT worm tea. In fact, it can be toxic to both the worms and plants. But the clincher is that it also appears to be toxic to the fish.
I was hand watering the buckets up until just the last couple of days when I installed the drip system. Each time that there was significant runoff through the collector drain into the Biopond the next day there would be one or two dead goldfish. If I collected the runoff in a bucket and not allowed the runoff to go into the Biopond no dead fish the next day. I repeated this several times each time with the same result.
I have never worked with closed systems before where there can be accumulative toxins. The plants do not purify the water they just remove the substances they can utilize. In an open system, the plants also use the substances they can utilize, but the other pollutants or substances are eliminated as effluent.
The plants in the buckets are doing fantastic as they should be. The discharged worm runoff is now dumped into the compost pile or diluted and poured on the yard. Hopefully there it will do some good. Bottom line is I will maintain the worm bucket garden separately from the aquaponics. I will add the lacking nutrients, such as calcium, iron, and magnesium sulfate as needed to the aquaponic system.
I will continue to add a few red wigglers to the grow beds to break down any fish waste solids. But, because the water circulating system included 8 lbs of red lava rock as an under gravel nitrification bed in addition to the lava in four of the grow beds the fish waste will not settle out as it would in a bare bottom fish tank. I am not certain if the worms will even survive.
This is not a controlled study, it is observations only. I am putting this out as a precaution, your results may differ, however, if you duplicate what I have done, do so with caution.
My jury is still out on the validity of Vermiponics. When I started this project, I was aware that worm castings are purported to be toxic to worms. Liken to us as human beings living in our own sewage. I proceeded using the rationale that with each bucket having a plant growing in it, the concentration of substances in the bucket runoff would be diluted to the point of being a benefit to the total Aquaponics system. However, certainly on the scale of worm ratio to plants and fish, it appears to me to be too much.
Possibly one or two buckets would have worked or a much larger number of Grow Beds. I will continue with further experiments to see if Vermiponics can be a viable asset to Aquaponics. If and when you attempt to do Vermiponics with Aquaponics, contrary to a lot of what is printed, the quality of the worm castings and the concentration of substances in the runoff vary according to what the worms are fed.
Worms fed a heavy diet of newspaper and cardboard produce worm castings that are very low in nutrients compared to those that are fed a rich diet. It is much easier to sell Vermiponics with the let’s be green crap, help the environment, and get rid of your newspapers by buying our worms. If you want to help the environment stop buying the newspaper, magazines, and try to get legislation to put a ban on junk mail.
A caution on Vermiculture; there is a tremendous amount of information on the web. Much of this information is akin to snake oil claims as there are a tremendous number of scams still related to Vermiculture.