Many people have fish ponds. Some are simply decorative and others are to raise fish for market or to feed the family.
This Instructable is aimed at increasing the productivity of small scale fish ponds. It's really cheap to make, so I actually think that this concept could be used to help boost the protein available to subsistence farmers and small communities in developing countries. It could of course also be also used to help feed goldfish in a decorative pond too.
The idea is to use a light source to attract flying insects at night. The insect's navigation is disturbed by the light, and the insect spirals into the water where it instantly becomes fish food. The fish grow fat, and in turn provide food for humans.
The idea isn't new; I saw a similar design in a permaculture magazine many years ago. All I have done is utilize a cheap solar LED garden light and recycled materials.