Space required to grow 36 kg beans and 60 kg sweet corn?

Question

I want to build an aquaponic system, that would suffice a family of 4 all year round. I would like to know what space would be required to build the system. Moreover, what should be the size of fish tank and grow beds for the plants? Thanks.

Answer 1

Former aquarist here and I did try to do hydroponics by growing things on top of my fish tanks. There are several things to consider there.

• Tilapia grow larger, about 12 inches. The size of your tank will be the size for full grown fish, not for the babies.
• The bigger the tank the better for several reasons. The first grow bigger, the waste is spread out more (though you still need a filter system), and the temperature is more stable in a bigger tank with more mass.
• Will you need to heat the water during certain times of year? If so you need to get a bigger heater than your tank. If you have a 100g tank you will need a heater for 120 gallons for those unexpected extra cold days.
• What about cooling? Does it get too hot in your area for the tilapia? If so you will need a chilling system of some sort. Or put the tank in your basement if you have one.
• Smaller tanks with too many tanks cause increased stress for the fish, leading to disease, stunted growth, and more concentrated wasted. I don't recommend it.
• You must understand how a closed ecosystem like this works, and how fish waste (ammonia) is turned into nitrites and then to less harmful nitrates which can be used to feed plants. Understand that the water tests are important, and test strips expire and are also more expensive than the drop tests per test. The drop tests are cheaper per test, last longer after opening, and are more accurate.
• Keep notes on what you learn. There are several free Windows applications to track notes in a tree-like or wiki format. Tiddlywiki.

More info

• Video on aquaponics in India. This has links to more videos of a similar nature.
• This Google image search can help you find ideas on how to build it using different materials.
• Aquaponics in India. You might get some more handy info here.
• A forum post about aquaponics in India. That forum might be helpful for you.
• UrbanFarmingGuys looks like small scale aquaponics. They have a forum and a wiki.

Answer 2

I'd advise against growing corn aquaponically to feed your family. Consider that you need to space the plants out about a foot, and say one plant gives you 1 kg for ease of calculation, and that you can grow 3 crops per year, then you'll need 20 square foot for each crop, which is a pretty large grow bed.

Consider also that the bulk of the corn is in the roots, stems, leaves and cobs. The only edible part is the kernels. But you have to buy in fish food to feed the fish enough so that they produce enough waste to provide the nutrients for all that largely wasted plant material that you can't use. Now a farmer would put that material back into the ground for composting, but you can't do that unless you also have a farm.

The best crops to grow in this expensive manner are those where you can eat as much of the plant as possible.

In terms of energy density, the best crops to grow are root and tubers such as potatoes, sunchokes, turnips etc but they are not suited for aquaponics. So, you're better off growing leafy vegetables that you can then exchange for these other vegetables.