They're not difficult at all. However, they require being introduced only into well established aquaria with lots of invert colonies (copepods, amphipods, etc) to graze on. Raising pods in a refugium will help in replenishing the main system. If the tank isn't well established, it's recommended to have cultures, in different development stages, of pods growing in culture bottles, jugs, vats, etc. to provide enough food for these constant grazers.
Meet the diet requirements and these mandarin gobys will give your tank a splash of colors hard to find in other species.