microscopes for koiUsing a microscope is an essential part of koi keeping,parasites are the scourge of all koi hobbyists and must be kept in check,if left unchecked big problems will accrue for sure,there are quite a few different types of microscopes and most parasites can be detected with a magnification of 40 x (=10x ocular and 4 x objective,costia are optimally visible with a magnification of 100 x( = 10 x ocular and 10 x objective.
Parasites in fish are a natural occurrence and common. Parasites can provide information about host population ecology. In fisheries biology, for example, parasite communities can be used to distinguish distinct populations of the same fish species co-inhabiting a region. Additionally, parasites possess a variety of specialized traits and life-history strategies that enable them to colonize hosts. Understanding these aspects of parasite ecology, of interest in their own right, can illuminate parasite-avoidance strategies employed by hosts.

Usually parasites (and pathogens) need to avoid killing their hosts, since extinct hosts can mean extinct parasites. Evolutionary constraints may operate so parasites avoid killing their hosts, or the natural variability in host defensive strategies may suffice to keep host populations viable. However not all parasites want to keep their hosts alive, and there are parasites with multistage life cycles who go to some trouble to kill their host. For example, some tapeworms make some fish behave in such a way that a predatory bird can catch it. The predatory bird is the next host for the parasite in the next stage of its life cycle.

Costia,White spot,Tricodina and flukes are the most common and need to be addressed quickly.