Randy, I've done some thinking about the closed loop represented by grubs eating fish/fish eating the grubs, and my guess is that it's not a problem. I think that because of the dynamic you find in the pond in first place where every species is feeding on every other species including their own kind. In other words I'm picturing the pond as a closed loop itself, or at least somewhat closed if that makes sense.

For example; BSF grubs eat a small fish from my pond and then other fish eat those grubs. The fish that eat the grubs could have just as easily eaten the fish that were fed to the grubs, depending on their size. Parasites or pathogens would be passed from fish to fish as they eat each other, and inserting the BSF into the chain doesn't seem like it would change much IMO.

Having said that, injecting BSF into the equation might actually lessen the survival of pathogens/parasites. Tests indicate that BSF reduce e. coli and salmonella in food waste. The digestive system of BSF grubs is extremely powerful, lowering the survival rate of pathogens.

There are also studies that indicate that the mature BSF grubs secrete an anti-biotic. I'm not completely sure about the accuracy of those studies, but I'll look into them again and report back.

I do have some first hand evidence that the BSF might reduce some parasites in the food chain. I first mentioned this almost 2 years ago in this same thread: http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=87545#Post87545

It seems that the fish I fed to the colony at that time had a living parasitic worm in it. I think the BSF grubs ate the fish but avoided the worm. If that parasite came from the fish then it does represent removal from the pond. I assume it did come from the fish because that was the only animal I had fed to the colony. Here's the photo showing the parasite which is near the anal fin:

(click to enlarge)


Even though the BSF didn't necessarily kill the parasite it's not likely it would survive in the colony or that it would make it back to the pond. I suppose it's possible that the worm could get into a grub, but I have strong doubts about it.

I'm aware of concerns about these types of loops with regards to fowl and mammals, but my guess is that fish are different. I think it might have something to do with the fact that fish are basically cannibalistic. I'm interested what you all think about this.