I found this article about why goldfish are bad for african clawed frogs, I'd assume its the same for toads:

Can Clawed Frogs Eat Feeder Goldfish? | Animals - PawNation

and another one about feeding goldfish to turtles:

Feeding Fishes to Amphibians and Reptiles: the Goldfish /Vitamin E Question - Part 1

as for spiders I have no idea!! Now you've got me curious