During the last 5 months, a very exciting and unique project has been underway here at Nourish the Planet/the Center for Sustainable Aquaponics. When I started my internship, one of the first things I learned about aquaponics is that the feed is one of the most important inputs to the system. Adding anything to the system costs money, of course, and feed is one of those costs that seems unavoidable, right? As I began researching different options for feed, one particular method struck me as a brilliant and cost effective, although underdeveloped, way of generating feed, by converting kitchen scraps into fish food using the black soldier flies. Thus, the black soldier fly (BSF) project was born, and I set forth on a mission to learn everything I could about this new insect and its potential benefits.
Soldier fly composting is a relatively new practice in the modern world, however, there is a seriously committed group of people compiling information online in the form of many blogs, websites, forums and videos. As I scoured the web for information, I quickly found out that raising these little bugs can be a bit tricky. For starters, the BSF is a sub-tropical species. In areas of the world where they live, composting with these insects is as simple as providing a food source for wild females to lay their eggs nearby. In other parts of the world however, the system has to support each stage of the life cycle in captivity. Although the odds were not in our favor, we decided to go for it anyway figuring that if all else fails it would still be a good learning experience. In December, 5,000 medium size grubs were purchased online for the low price of $80 and placed into an enclosure designed to provide the necessary conditions. It soon became obvious that the largest obstacles were heat and humidity as the health of the grubs quickly deteriorated. The population dropped to about 1,000 grubs over the next few weeks as we tried different methods of adding heat and moisture. Over the course of two days, the remaining grubs were collected and transferred into a smaller container to condense the population. After a week in the new enclosure a large amount of grubs had become mature enough to begin the breeding experiment. About 300 mature larvae were placed into the breeding container, a clear plastic storage tote lined with sawdust and sponges for moisture. 3-4 weeks passed before about 25-50 adults emerged and began to mate. Of these mating adults, only 2-5 females laid eggs, which hatched a few days later. Each female can lay up to 500 eggs, so at the moment there are 1,000-2,500 newly hatched larvae in the breeding container.
Since the project has started, we have succeeded in supporting the grub life cycle to allow grubs to grow into mature prepupae. We have also gotten grubs to undergo metamorphosis into adult flies. We have bred the adult flies and provided conditions that stimulate females to lay eggs. Eggs have also hatched, successfully starting a new generation of captive soldier grubs. The next stages of the project will include raising the newly hatched larvae into maturity and breeding the adults again. This process was highly inefficient the first go around, so hopes are high that this time the specific environmental conditions will already be met, preventing loss. So far we have demonstrated that the soldier fly can be raised in Colorado in the middle of winter. We believe that if the process is scaled up and perfected, that sufficient amounts of soldier grubs will be produced. This allows for a steady population of adult flies can be maintained to breed and lay eggs and a steady supply of grubs can be generated for use as fish feed. While no feeding trials have been conducted, we are confident that conditions can be met to support production of this insect in non-native regions in order to substitute the cost of traditional fish feed.
-written by Mike Lolley, Fisheries Intern, Fall 2011