Please give me some specific reasons. And specific differences in needs of vamps Vs frogs. No one has listed a reason other than "it's just something we don't do"
Since you want to be spoon-fed the issues that can arise from this particular type of mixed enclosure as opposed to doing your own research and coming up with reasonable conclusions, I'll oblige with suggestions based on my own experiences and information gleaned from those wiser/more experienced than myself . I don't necessarily think it will prevent you from doing what you want, but it may assist some other keepers pondering the same kind of display from making the same mistake.
I am going to create a combined dart frog and vampire crab vivarium. It is a 10 Gallon terrarium (not ideal size) I willl be looking to upgrade size in the next 6 months
It will contain 2 Auratus and 2 vampire crabs.
My mind is made up. Unless everyone really thinks this is a terrible idea i am going to try to house them together
Reasons i think it will work
Dart frogs and vampire crabs are kept in identical habitat and identical temperature/humidity range
What are you basing this on? Dart frogs from where? Vampire crabs from where? There are HUGE variations in environmental conditions within the ranges of Dendrobatids, and likely Geosesarma as well. My crabs have done best cooler than my frogs, I generally keep them 65-70*F.
You mentioned D. auratus as your frog of choice, which locale/morph?
They do not cohabitate in the wild but the care sheets for the two animals are almost identical.
Where are you seeing these identical 'care sheets'? What kind of information is presented?
My dart frog set up already contains a small pool.
Is this the primary reason that you wanted to include the crabs? Because there might be a tiny little niche in your tiny little tank that could possibly support them?
The crabs are not nearly large enough to harm the dart frogs
You didn't answer my question about ever keeping vamp crabs before, and this question baffles me. I've kept two forms of Geosesarma sp. in the past, and they would go after my fingers if they were hungry or agitated. The adults have strong enough pincers to catch and dismember each other, and they would certainly have no problems snagging an auratus (at least long enough to remove a foot or an eye). Additionally, if you had any breeding from either species, the young would certainly prove to be prey items for the other species.
Yeah, sort of. The crabs are omnivores, which means they will forage just about any plant or animal based material around them that they consider edible. They will pay particular attention to moving prey, and frequently become more aggressive when it is present. This means that the crabs will be most active and nasty exactly when and where the frogs are being fed.
Vampire crabs are nocturnal, they will be burrowed in one of my coconut huts during the day and active at night when the forgs are asleep.
Can't say that I've seen much of a difference in activity level between when lights are on or off. They will be out when they want to, and they will occupy the space they feel most comfortable. I doubt that it will be inside a coconut hut, unless there is nothing more suitable in the viv.
The crabs will need as much shoreline space as you can provide, with multiple, deep inset burrows along, but not under the water. The closer their quarters, the more often you will lose individuals.
Any more specific questions? Or answers to mine?