In general, Josh's Frogs is against mixing species (and even morphs of the same species). It's best to make sure we house different species of dart frogs in their own vivaria, as they can easily outcompete each other, or even crossbreed in some cases!
There are some other animals that, in the correct circumstances, can do well housed with dart frogs. These animals have similar needs, but they are different, and we have to be careful to understand and meet those differences. We're all probably familiar with mourning geckos, which take readily to a humid tropical vivarium, and are more than happy to chow down on fruit flies and fruit. You can read more about their cohabitation here.
There are several smaller species of tree frogs (lemurs, bird poops, hourglass, and clown tree frogs, all arboreal and active at night) that can do quite well with some dart frog species (terrestrial and active during the day) when set up properly. These tree frogs are best kept with leucs, auratus, and tincs—we'd recommend against cohabbing with most Phyllobates or thumbnails. Make sure the dart frogs are at least 2/3 grown, as ideally they'd be able to consume any extra crickets the tree frogs may leave behind.
Sounds cool, right? It is, but only when it's done right! Oftentimes, constructing a vivarium to house tree frogs with darts will take more time (and be more expensive!) than setting up two separate vivaria. Cohabbing can be done, but it's not for everyone. Here are some things to think about:
Always select captive-bred animals whenever possible, but this is even more important when housing different species together. Wild caught bird poop frogs, hourglass tree frogs, and clown tree frogs are still commonly available (in fact, most available at pet stores and reptile shows are probably wild caught). They may carry all kinds of pathogens and parasites that would prove harmful to your darts, not to mention Chytrid fungus or Ranavirus.
Many people have the impression that keeping multiple species of frogs together in one tank would be less work than housing them individually. I'd beg to differ! You need to be familiar with the care needs for any animal you keep, but when cohabbing you also need to be able to address all of those needs in one enclosure, and do so in a way that will not harm the other inhabitants.
Below is a chart showing some of the care differences between dart frogs and the small tree frog species discussed in this blog. It's very doable to meet all of these needs in one enclosure, but it will require intent, research, and a bit of spending.
As you can see, when housing dart frogs and tree frogs together, you'll now need to provide ventilation and UVB (goodbye solid glass top!), feed crickets at night as well as fruit flies during the day, provide standing water (if it's in a dish it'll need to be changed daily), and ensure the enclosure can provide the proper temperature and humidity gradients needed.
Dart frogs are primarily active on the enclosure floor, while the tree frogs will need large, smooth leafed plants (such as Pothos or Philodendron). Constructing such an enclosure will take planning and effort, and it's going to need to be larger to meet the needs of the inhabitants. Think 50 gallons+ to start, and go bigger if you can.
As stated above, go big. The last thing you should do is simply throw some tree frogs in a small, preexisting dart frog vivarium. They will not do well for you.
Think of starting with at least a 50 gallon or larger enclosure. You'll want it to be at least 24 inches tall (36 inches is even better!) in order to provide a proper humidity gradient—higher humidity towards the bottom of the enclosure where the dart frogs will be active, and lower humidity (no lower than 60%) towards the top of the enclosure, closer to the vented top. The tank should be at least 24 inches long, to allow ample space for all inhabitants to move around.
These tanks take planning. Be ready to spend time researching before you begin construction, and take it slow. Set up the tank and allow it to grow in and run for a month or two before adding any inhabitants, taking temperature and humidity measurements along the way to ensure the habitat is really dialed in.
I'd recommend adding darts first, and doing so several months before adding any tree frogs. This will allow the dart frogs to grow up a bit, and have a chance at taking down any spare crickets the future tree frogs leave behind.
If you choose to do this, be ready to spend time ensuring your community is behaving as expected. Are dart frogs out, active, and eating during the day? Are tree frogs only active in the evening or at night, and spending their time in the higher reaches of the tank? If the animals are not maintaining proper body condition or are acting unusually, be ready to pull the plug.
We've found that dart frogs and smaller tree frogs together tend to coexist well with the proper planning, set up, and care, but make sure you know what to look for when a community is failing to thrive.
Yes, smaller species of tree frogs may be housed successfully with dart frogs in the proper conditions, but it's not for everyone. If you're willing to do the research, spend the time and money it takes to put together a large, complex vivarium that meets the needs of the inhabitants, and carefully observe your pets to ensure success, it might be right for you.