roflmao.. I knew I shoulda kept my original comment.. aka your gonna get crap for feeding live from some. But imo live food is apart of a healthy balanced diet. be that "live food" frozen,feeder fish, zucchini, worms, ect.. I'de be most concerned w/ bacterial fungal possabilities, and any live feeders caught can hold contaminents such as fertilizers, pesticides, ect..
and I do not recall the cubans haveing any type of toxin. the majority of toads do though. But they are rarely lethal or even harmful long term (the exception being a few of the poison dart species of frogs). and fish will spit them right back out unless starved generally. I'm not 100% so i would do some research on feeding the species before doing it. which is common sense imo.
EDIT: The problem with the link and what was stated.. is it lists a variety of predetors who are unaffected by the toxins, but that humans and pets should avoid them due to the irritation caused by the toxin. you'de be surprized how many creatures have "toxins" that do not effect other species, or are immune. Persoanlly though I wouldn't continue feeding them unless I found exactly what this toxin did, and it's impact upon fish. ie if a build-up of this toxin could occur in the pets body and kill it. or if it is harmless.
The Sticky about feeders is a fount of info as well. No i've never fed frogs, because it hasn't been practical but I've heard many Arrow keepers swear by them.
100% live is not neccisarily healthy, but neither is 100% pellets imo. Variety is key as our pets can't go search out what they nutritionally need.
My Oscar also loves crickets, minnows, pellets, frozen bloodworms, frozen mysis( def not his fav but will eat), and has decided to try the earthworms I feed my fire eels. And would keel over from stuffing himself with krill if i let him. frozen and/or freezedried. about 50-60% of his diet is pellets and the rest is something or other.