Derek Stobbard wrote me an email with this idea for nutrients:

“Here’s an idea for natural nutrients: Keep fresh water fish – goldfish, for instance. Once a week empty one fifth, to one third of the water from your fish tank and replace it with new water (preferably water that has sat in a bucket for a day – to get rid of the chlorine). Empty the water you took out of the fish tank into your watering reservoir. This water will be rich in nitrates from your fish’s “waste” which plants love, and if you feed your fish sustainable and organic food, so much the better. As long as you are doing this regularly, your fish water should not smell. Beware of algae, keep your fish tank out of direct sunlight, as algae will consume the nutrients and the oxygen from the water.

If you grow anything other than green leafy plants you may need to add very small amounts of calcium, iron and potassium from time to time (once a month). However, you may get away without it since you use clay pellets as a solid medium in your pots, and this has trace amounts of these necessary elements. Also, depending on the food you give your fish, some of these may already be present in the uneaten food, and will make their way into the water. ”

I love the idea and generally love the idea of aquaponics (fish + plant system). I continue to remain skeptical about incorporating fish into the windowfarm because forcing symbiosis between two different ecosystems is pretty complicated stuff and the balances can get out of wack really quickly meaning you could end up with a bunch of dead plants and fish really fast.

I like that he proposes simply using the fish water as a nutrient source and moving that water to the windowfarm after a simple filtration process. Anyone want to try it out? We would need a control group as well. Build two airlift systems- one using fish waste and the other using the recommended (Sugar Peak Organic Hydroponic Vegetative Nutrients) commercial nutrients? That would be rad, guys.

Remember everyone, creating nutrients is a pretty sophisticated biochemistry application so you gotta be ready to be super experimental. You probably will lose a lot of plants along the way. If you just want beautiful veggies you can eat asap, start by experimenting with existing hydroponic nutrients and only make slight modifications to start with.