If you frogs are very rare I don't dare to guarantee anything. BSF are an integral port of nature's decomposition process together with so many different species of bacteria and fungi.
One could argue that healthy black soldier fly colony will give you the lowest risk of a pathogenic outbreak.
As you might have read in this post, BSF allow for uber fast break down of organic matter while inhibiting other putrescent factors to dominate the waste pile. If not the decomposing matter would become anaerobic and stinky in a matter of hours. Also they redistribute moisture and keep the decomposting matter from turning thermophillic (115 - 160 degrees F)
So predominantly the BSF provide for all the right ingredients for mesophilic bacteria (50 - 115 F) to dominate.
This does not guarantee that pathonogenic bacteria or protozoa can not be introduced to the system and "survive".
However, BSF have a unique process in which they migrate and clean themselves prior to pupation. They empty their guts completly... getting rid of their entire digestive track and mouth part. It's at this stage that it is believed that they secrete an anti-bacterila agent of some sort prior to pupation.
So, it's fairly accurate to say that the soldier fly pre-pupae are as clean as possible.
Therefore a contraption like our biopod not only keeps conditions optimal for the active black soldier fly in the colony it is also a device for seperating the pre-pupae from the decomposing matter.
If I were you, I would try to set up a colony in a well shaded portion of your yard away from the frogs. I would then harvest only the pre-pupae and preferable keep them in stasis for a few days prior to feeding them to your frogs. keeping them in a small tray filled with wood shavings in a shed would be fine.
If need be, you can always try to disinfect the pre-pupae as this will not kill them.
Also I would be very selective on what I put into the colony. I would put in only food waste from human consumption. UNDER NO CIRCUMSTANCE would i introduce any organic waste that had been in contact with your frogs. Many "frog" pathogens live near your frogs and on their waste and the last thing you want is your colony to become a breading ground for their pathogens.
Without the foresight to what pathogen may or may not be present? I would start small. I hope that these guide lines can give you some sort of "best practise" advice.
