That’s good advice; a lot can happen in a month. I don’t use the liquid so I modified my original BioPod with a straight drain. It’s worked like a charm and you can see how I did it on my “tips and tweaks” page: http://blacksoldierflyblog.com/biopod-tips-and-tweaks/. I highly recommend using a pre filter also, either coconut coir as I show on the same page, or a synthetic. With the straight drain and the pre filter I could pour a few gallons of water into the unit and it would drain in minutes.

BSF could do fine on nothing but bread, so it isn’t the type of waste that’s the issue, but you’re probably right about the quantity. Bad odors indicate a system that is out of balance and that will only get worse if you don’t correct the problems that caused it to become anaerobic in the first place. I believe the two main reasons for a BSF colony becoming anaerobic (sewer-like odor) are poor drainage and overfeeding.

Drainage: I think the only way to have good drainage in a BSF unit is to have a filter medium that covers the entire bottom of the unit. I’ve described using coconut husk fiber (coir) in several places, but I’m also testing synthetic air conditioner filter material now. It’s possible to operate without drainage, but you must be careful not to add too much waste with high moisture content. Alternatively you can soak up excess liquids with dry waste items like cereals, or with wood shavings/sawdust. A proper drainage system provides the best results and the most convenience.

Overfeeding: Besides causing anaerobicity, overfeeding can also result in undesirable fly species being attracted to the unit. BSF repel other species in a balanced system, but excess rotting food can nullify this effect. It takes a lot of larvae to process a lot of waste, and to operate a BSF unit near it’s maximum you need a population that equals 2-3 inches (5-8cm) of solid larvae. On average waste should be consumed in a day or two. Items like soft fruit, cooked vegetables/grains and fish should be gone in hours, and hard items like raw vegetables, and hard fruits might take several days. In a colony that is sufficiently dense any rotting food will be consumed very quickly because at that stage it becomes soft. This rapid consumption of any rotting waste is one reason that a BSF unit should not have a bad odor; bacteria doesn’t have time to multiply before the waste is eaten.

An anaerobic system is in a downward spiral with regards to BSF because BSF females are not attracted to these conditions. You may get some eggs laid in the unit depending on the extent of the problem, but not as many as if it were in a aerobic state. If you live in an area with a good population of BSF you might consider starting over with an improved drainage system. You could collect some BSF from your current system and use them to seed the new one: http://blacksoldierflyblog.com/2008/07/25/collecting-immature-larvae/. You can also try salvaging what you have by drying the waste out and adjusting the amount of new waste added. It would probably be best to stop feeding at all until the anaerobic conditions begin to lessen. The problem with salvaging what you have now is that it doesn’t address the deficiencies of your BSF unit.

Thanks for sharing your experience and please let us know what you try and how it works out.

I’m sure it’s possible to eventually drown a BSF larva but it would be difficult. I’ve found larvae thriving in containers of seed corn that have been flooded for several days. As long as the larvae can reach the surface they’ll be fine indefinitely.

If your weather turned cool it might be that the larvae are buried, waiting to warm up so they can become more active again. Also, in an open system like yours there will be times when large numbers of larvae migrate away. I assume this happens because conditions in the pile become less than optimal, e.g., too hot, too little food for the size of the colony, etc. There is also an ebb and flow to a BSF larval colony and I assume an open system would experience greater fluctuations than one which contains the larvae.

If most of your BSF have moved on don’t worry, just keep adding waste and they’ll be back to lay more eggs soon.

I still haven’t found a simple method for separating larvae from compost. You can remove most of them but getting the last 5-10% is a challenge. The juvenile larvae can be attracted with food so you can direct them the way you might do with worms, with desirable food scraps in one corner. You can also use this technique: http://blacksoldierflyblog.com/2008/07/25/collecting-immature-larvae/

The dark mature larvae don’t eat so you can’t use food to attract them, but if your unit has a self harvesting system the majority of those larvae should remove themselves.

If you plan on using the compost outdoors you really don’t need to worry about getting every last larvae; any left in the compost will simply crawl away. The larvae aren’t able to consume fresh vegetables so releasing them in a garden isn’t an issue.

Right now I am only using the tea which filters through the bottom of my system. Any help would be appreciated.