Greenbackyard

  

Test kit, originally uploaded by brunom.

The system has now been running for a while, the fish are growing very well and so have the plants (some more than others).

I purchased the kit you see in the picture a few months back, thinking that I should test the water immediately to make sure that we were going down the right path. I just let it slip and since the fish seemed very happy and the plants were growing, I assumed that everything was on track.

Yesterday, I finally took some courage and tested the water since I was planning on taking the chard out of the system to eat it (that’s the whole point, right?). I ran every single test that comes into the kit, i.e. pH, ammonia and nitrites levels and carbonate and general hardness.

pH = 7.4
Ammonia = 0 mg/L
Nitrite = 0.1 mg/L
Water is soft and carbonate hardness is 20 mg/L

The results show that the fish are not generating enough ammonia to cause toxic levels of any sort. In 500L of water, those tiny Silver Perch (only 10 of them) is not enough density to cause problems. That’s my conclusion so far.

Of course, this has also its downside, i.e. not enough ammonia == not enough food for the nitrifying bacteria and, as a consequence, not enough food for the plants. Which explains something that both Danielle and I had been considering for a while. The plants are growing however we are not experiencing those “dramatic” growths as described by the multitude of aquaponics practitioners around the world. We thought that the lack of sun would also be a problem however, since we moved the growbeds into a much sunnier spot, I believe that lack of sun light is no longer a problem and, if that was the case, we probably would have higher levels of ammonia or nitrites in the water (i.e. the plants wouldn’t be growing well, not due to the lack of nutrients but due to the lack of light).

So far, I am very happy with how this prototype aquaponic system is going!

Marigold, originally uploaded by dhickie.

One of the best things about planting a marigold or two in our aquaponics system would have to be the wonderful burst of yellow that greets us everyday when we look at our lush beds. Marigolds are more than just beautiful though - traditionally Marigolds are planted in the garden because of their beneficial qualities. French marigolds have a very strong odor which confuses pests, and their roots give off a substance which repels nematodes.

Don’t quite know your nematode from your left foot? Well, a nematode is a tiny (microscopic) lifeform. They are the most abundant multicellular lifeforms on earth. In a teaspoon of garden topsoil there might be millions and millions of nematodes. “Depending on the species, a nematode may be beneficial or detrimental to a gardener’s cause. From a gardening perspective, there are two categories of nematode: predatory ones, which will kill garden pests like cutworms, and pest nematodes, like the root-knot nematode, which attack garden plants.” Wikipedia. So in a traditional soil based garden, you plant marigolds to repel ‘bad’ nematodes which build up in the soil after some crops such as tomatoes.

So how effective are marigolds in an aquaponics system? So far, we’ve noticed a few interesting things. Firstly, the green caterpillars that are our current uninvited dinner guests every night seem to love eating Marigolds even more than they like eating our plants. So they seem to be drawing the pests away. Additionally, the caterpillars seem to want to cocoon in the Marigold leaves - another service to our other more desirable food crops. And as I learned on the Milkwood Permaculture course I did earlier this year, its not always necessary to have a pest-free environment. It’s better to have an environment that supports life, a balanced system, rather than a sterile system devoid of insect life, so admired by farmers who farm monoculture crops.

There is always the chance that the Marigolds we have are hybrids, and are therefore less effective than the older and stronger varieties. As for the nematode repelling qualities of the root system, that’s an interesting question when it comes to aquaponics, a non soil based system. I’m assuming there are nematodes in the gravel beds, but since the system flushes out every hour or so it wouldn’t be the same as a soil based garden, which would naturally see some build up in soil substances. Classic gardening concepts such as crop rotation address this particular issue of how to organically balance soil nutrients. In terms of nematode build up though, I don’t yet know much about this area and I’m keen to look into it over the next few weeks.