A World Unto Thier Own

We get questions from time to time, asking why we advise against keeping fish & frogs together in a standard Aquarium setting. While African Dwarf Frogs are a popular addition to freshwater aquariums, it's not always a good thing for either the fish, or the frogs.

Too often, the choices of what species are together in a tank, is determined by owners preferences, often whether a fish is pretty or cute or even how "happy" a critter seems when seen in a pet

Oooo! There's one that matches the wall paint!

shop tank.  Unfortunately, a tank owners personal preferences is the WORST yardstick to use. The compatibility of different species should ALWAYS be considered over anything else. Always consider the type of fish species indigenous to the natural habitat of the frog... In other words, if you have African Dwarf Frogs, ALWAYS choose the species of tropical fish that are also indigenous to West African rain forests over all others.  Why?
Because eons of evolution has naturally selected fish & frog species to tolerate diseases carried by each species, who have evolved together in the same regional environment. A frog evolved in West African Rain forests, may not have tolerances of disease vectors carried by tropical fish from South East Asia or elsewhere. 

Hey! This oriental food is pretty tasty!

Equally important, is natural behavioral traits of each species, imprinted by location and circumstance, which are now instinctive.  While species may have naturally tolerant behavior regardless of where it evolved, some may have behaviors that will clash or compete with a foreign species, all because of where each species evolved from, and the environment each evolved in.
 Regardless if animals are bred in captivity or in the wild, evolutionary behaviors & physical tolerances do not radically change. Disease susceptibilities within a species still reside, whether bred in the wild or in captivity,  & there are cases where the presence of a foreign species can actually create susceptibilities which would normally not be present.

Bloat, (Dropsy) is a good example.  There's still no conclusive reason why ADF's lymph nodes are triggered to overproduce lymph fluid. Some suspect a reaction to a common bacterium, often found within the skin layer of tubal worms, like blood worms. Yet exposure to this bacteria in nature seldom shows ill effects. Bloat is not a common disease in nature, not near as common as it is in aquariums. However, there's evidence that ADF's sharing an aquarium habitat with fish, have a higher susceptibility rate than do ADF's who do not. One conclusion would be that something common with some fish species may tie in with exposure to the bacterium, which normally would not pose a problem, since intermingling to such species would never happen in the wild.  Another conclusion may be environmental factors, common within a fish friendly habitat, such as higher dissolved oxygen content in the water, can cause abnormal susceptibilities in African Dwarf Frogs, or a more tolerable environment for the bacterium to thrive & concentrate.
Remember, frogs can coexist with fish in an environment tolerable for fish, yet in a natural environment of extreme acidic, nitrate high, & low oxygenated water, fish are not a common species to co-exist with these frogs. Most fish cannot tolerate water conditions these frogs would call home. It's entirely the reason that in a more pristine aquatic world of a freshwater aquarium, species of fish & frogs which naturally never be together do intermingle, and present possibilities that never would happen in the wild.
These are the reasons we run contrary to conventional wisdom, and advise keeping fish & frogs separate in a aquarium environment. Doing so allows maintaining a tank ecology most suited to the needs of a species, while keeping the likelihood of cross species contamination & behavior conflicts totally eliminated.