Creating a self-sustaining (or very nearly so) habitat for tree frogs and fish can be very time-consuming, but very rewarding in the end…
Begin by deciding what sort of environment you wish to create and what sorts of critters you’d like to put in the tank. This is extremely important, as many frogs and fish are only compatible with certain environments and species. For example, my tank has White’s Tree Frogs. These are large tree frogs from Australia – they can reach sizes relative to a small adult fist and are cannibalistic, meaning they’ll eat other frogs (even of their own species) if those frogs are small enough to fit in their mouths. White’s will also eat lizards, newts, salamanders (which is why newts and salamanders should never go in the same tank with frogs – if eaten, they are toxic!), along with their normal diet of insects. Therefore, I can only have White’s Tree Frogs of SIMILAR size in my tank and nothing else. If I’d wanted multiple frog species, it would have been necessary to choose something else…
As far as basic tank set up goes, it is again necessary to choose your critters ahead of time, as some may prefer more land, some more water, some more height, etc. Again, I’ll use my tank as an example, as it is easiest. White’s are tree frogs that get rather large, so I chose a tall 29 gallon tank – I only have three frogs, so this is plenty of space.
Being tree frogs, White’s require LAND, so I backed the tank with cork bark and stacked up the sides with rocks and caulked the gaps with moss (excellent for keeping the humidity up). I created ledges and caves and placed large branches in the tank to give the frogs numerous vantage points and places to hide (they’re nocturnal and like to hide out during the day). I also built a small waterfall into the rocks – again, this is great for humidity, plus it keeps oxygen cycling through the water in the bottom of the tank.
The water depth in the bottom of the tank is another key element to these set-ups. You simply can NOT have deep water if you intend to have toads or dart frogs or something similar in the tank – you’ll drown them! Tree frogs have natural buoyancy, and therefore have little difficulty in navigating the 5-6 inches of water I maintain in the tank.
So, next step – as this is a self-sustaining (or nearly so) tank, I planted live plants in the gravel (underwater) and in the rocks and cork bark on the back and sides to provide oxygen. I don’t wish to get into the nitrogen cycle, but suffice it to say, the plants are necessary to create oxygen and convert the nasties the fish and frogs leave in the water and air. In addition, they provide organic matter (along with the dead insect parts that fall into the water) for the fish to eat.
Enter the FISH! I only have so much water in my tank, and so can only support so many fish – 5 is the lucky number for my tank, which is convenient, as I prefer small schooling fish like tetras (brightly colored and active!). Aside from the tetras, I also have one Chinese Algae Eater (or a snail, depending on circumstances) to keep the water portions of the tank free from nasty algae.
Finally, I use a UVB light to provide “sunlight” for the frogs, fish, and plants. Some people claim that you do not NEED one of these lights (the frogs are nocturnal after all), but experience has taught me that you receive longer life, better colors, and greater growth of all plants and animals involved when you use the light (never mind the fact that the light helps maintain a proper temperature in the tank!).
In the end, all I have to do is feed the frogs crickets on a regular basis. The cricket parts and plants feed the fish, who, in turn, feed the plants and clean the water. Plus, I have a really fantastic looking tank, with the soothing sounds of a waterfall, brightly colored fish to watch race around the pool area, and large attractive frogs that randomly leap and croak the nights and days away!