Goldfish are cold water fish that generally shouldn't be housed with most other aquatic animals. However, the African dwarf frog can make a good tank mate for your goldfish if your tank is large enough and you maintain the water properly.
Fish and Frogs
Frogs are amphibians, and most frog species spend significant portions of their time out of water. This makes them poor tank mates for goldfish because goldfish need fully aquatic enclosures. Most frogs also have vastly different temperature requirements from goldfish. Many frog species can grow significantly larger than goldfish and feed on goldfish as a primary nutritional source. Large frogs, frogs that require land and frogs that need high temperatures should not be housed with goldfish, eliminating most frog species as potential tank mates.
African Dwarf Frogs
African dwarf frogs are small, fully aquatic frogs that are docile and small enough to be housed with goldfish. They, like goldfish, require sensitive care and ample space, so avoid getting these frogs just because you want to alter the look of your tank. With proper care, however, African dwarf frogs can peacefully coexist with goldfish.
Tank Maintenance
African dwarf frogs prefer temperatures of 70 to 78 degrees Fahrenheit, while goldfish prefer temperatures of 65 to 75 degrees. To house the two animals together, you must keep the tank around 70 degrees. Both species require ample space. In small enclosures, they may fight, and the ammonia produced by each species can poison the other. Plan on at least 10 gallons of water per fish or frog, and set up a filter to remove excess waste. Drain 10 percent of the water each week, and change all of the water when it begins to get cloudy or smelly.
Avoiding Problems
If your fish or frogs get sick, remove them from the tank. Housing different species together poses some risks, as goldfish are more susceptible to disease from frogs and frogs are more susceptible to disease from goldfish. If you notice the animals chasing each other, they're not playing. Separate them immediately or you may end up with injured goldfish or frogs.
