My ACF have successfully murdered every fish that they've ever met. They devoured all the ghost shrimp I had and they even ate all the little ramshorn snails that were in the tank with them..

There is a chance to introduce disease with fish but really the biggest problem with ACF + fish is that a volume of 30-40 gallons limits you to smaller fish and they are food to your frogs, larger fish needs more water volume and they will usually attack and kill your or stress them out until they become ill.

Amphibians and fish just don't work 99% of the time. In the wild ACF will seek out bodies of water that contain no fish and will migrate out of fish infested waters to live in a fish-free pond. There are very good reasons for this, they have a better chance (as do their tadpoles) of surviving without fish around. So even mother nature says this is a bad combo. =)