“Hello. I have a quick question for you. I was wondering if on the aquatic side of the tank one could keep some sort of fish as well. I had a customer ask this question and my only concern was that the poison in the water that comes off of the frogs may harm the fish. Just wondering what your thoughts were.”
In some situations it is possible to keep fish with frogs, but other times it doesn’t work out. It depends on what kind of fish, what kind of frog, and how the tank is set up.
Although it is true that many frogs and toads are poisonous and have glands in their skin that can secrete or produce noxious compounds, normally these are not released unless the frog is attacked or feels threatened.
For instance, if you tried keeping an aggressive cichlid with a fire-bellied toad and the cichlid ate the frog that might harm the fish, but the toad simply occupying the same water as the fish won’t (side note— don’t keep cichlids with frogs).
But there are other considerations to think of as well.
The Right Environment
Although many frogs spend much of their time in or near water, accommodating fish can be challenging.
To do so you’ll need a large enclosure so you can create a water area of at least 5-10 gallons (minimum) for even just a few fish. Your average ten or twenty gallon aquarium probably won’t cut it. Think about it. If you have a 10 gallon aquarium and it is half land and half water and only half full, there may only be 2-3 gallons of water in the tank and that is not a large enough volume of water for keeping fish.
So, go big if you are trying to create semi-aquatic setup that incorporates both fish and frogs.
Also related to the environment is water temperature. The water will need to be heated in most cases so that it is warm enough for fish (although there are exceptions, for example white cloud minnows or gold barbs prefer cool water) and if the water is heated the temperature of the entire enclosure will probably not fall below the water temperature. Make sure the amphibians you are accommodating also live well at the temperature of the fish you plan to keep and vice versa.
Lastly, think about filtration. How are you going to filter the water for the fish? Submersible power filters are not especially powerful, though they may be the only option unless you plan on drilling a hole in the aquarium and using a sump.
The Right Frogs
It is also important to choose the frogs you keep carefully. Although you may be inclined to try this with semi-aquatic species, such as fire-bellied toads or a bullfrog, many amphibians that spend a good portion of time in the water may not be the best choice because they may eventually eat your fish. Frogs tend to be opportunistic in their feeding and if something moves near them and they are hungry they will usually try and eat it.
Aquatic frogs, such as African clawed frogs, are also risky inhabitants alongside fish. In some situations they may work, especially when kept well fed and in an especially large aquarium, but usually keeping fish with aquatic frogs is more like temporarily keeping frog food with aquatic frogs.
So what are the right frogs then? Often terrestrial species that do not go in the water will work best. If a large semi-aquatic setup can be created that has a land area large enough for the frog and a water area large enough for the fish, the two may not come in contact but still produce the desired aesthetic effect of a semi-aquatic environment with both amphibians and fish.
In this situation it is important to plant the water area heavily (and you’ll need strong lighting for this) and provide easy access to land so that frogs that are poor swimmers do not drown.
The Right Fish
You’ll also want to spend some time considering what fish to keep. Choose hardy species that do not need a lot of space. Fancy guppies can be a good option, though they are slow and may attract the attention of a hungry frog, depending on what type of frog you keep.
A school of a small hardy tetra might also work, given enough space, or perhaps zebra danios or cherry barbs. Whatever you go with, research its requirements well beforehand and follow the normal procedures for cycling an aquarium and/or use an aquarium product that introduces beneficial bacteria so that fish can be added without causing water quality problems.
Lastly, in many situations fish just aren’t going to work out. Perhaps the type of frog you keep is prone to eating fish. Or, the tank is just not large enough.
In these situations you might find adding shrimp or snails may be just as interesting as fish. Note that these aquatic invertebrates can be even more sensitive to water quality than fish, but if the semi-aquatic setup is well established and stable they can do just fine.
And, in the event your shrimp is eaten, you’re not out your favorite fish but instead you have just varied the diet of your frog.