Water mites in an aquarium are not harmful; in fact they actually aid the nitrogen cycle while providing tasty food source for small fish. If their population starts growing out of control then that could be a telltale sign something's amiss with your tank.
Rarely is it even possible to spot these tiny creatures; they usually move about in groups, hiding behind substrate or plants. But if one or more do show up in your tank, don't panic! Just observe and don't disturb.
Your fish should be delighted when you discover them; they're part of their natural ecosystem! Most aquarists take great pleasure in seeing healthy populations of copepods and amphipods inhabit their tanks - the closer your tank comes to mimicking its original environment, the happier and healthier its inhabitants will be.
These aquatic creatures don't rely on gills to breathe and can survive with very low oxygen concentrations, instead absorbing it throughout their bodies surface area. Furthermore, they can tolerate various degrees of pollution in water sources.
Nature provides aquatic invertebrates such as Hygrobates with an effective method for colonizing new bodies of water: by parasitizing other aquatic invertebrates such as chironomid larvae. Certain species of Hygrobates take advantage of bottom-feeding cyprinids' foraging activity to gain access to hidden chironomid larvae hidden inside sand tubes or hidden from view by using foraging as bait for their foraging activity.
Some chironomid larvae possess an exoskeleton that water mites find difficult to penetrate, forcing them to dig deeper into the sand in order to reach the larvae; this form of predation is known as active penetration.
