How much of a problem is this exposure of EDTA to my frogs?

[FrogO_Oeyes]

Many things are essential in "trace" amounts, but toxic [even highly so] at higher levels. Copper is one of those things which is well-established as toxic to amphibians [in other than background/trace levels].

For a wealth of references, google the following:
amphibia toxicity copper pdf

Those four words together, no quotes as the four terms are vital but aren't likely to form a phrase. "pdf" is added because most academic papers will be in pdf format. "Amphibia" is used in lieu of "amphibian" because the former is the term which will be used in ALL relevant papers, while the latter may or may not be. Substitute whatever other words you wish for comparable searches

[Herpetologic]

You might also look up ecotoxicology of amphibians. There are a number of books that have that in their title, and if you can get your hands on a copy it will go into greater depths such as WHY some of those elements are dangerous at specific concentrations.

Tangentially, I knew UofA was quite scrouge-ish, but I didn't know they were that tight, Adam. I don't know if it's because of my degrees, but I still have full access from my last alma mater and I haven't paid anything in years (albeit, maybe that's my reward for paying past tuition for those years I was in limbo...).

[lordoftheswarms]

Thanks for the responses guys. I will post what I find out, when I find out.