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i have noticed that many fish that i keep have black eyes, not eyes with whiteish, then a black pupil(or whatever fish have) Are they sick or what?

What came first? the chicken or the egg? No really.....

they are almost like eye caps....

What came first? the chicken or the egg? No really.....

What species?

The lens in a fish eye is pretty wide in some of the smaller species. They probably do have the white/silver section but it might not be easily visible.

http://www.schools.net.au/edu/lesson_ideas/optics/optics_wksht4_p1.html


For animals, the entire universe has been neatly divided into things to (a) mate with, (b) eat, (c) run away from, and (d) rocks. - Terry Pratchett

Guppies.... well pretty much livebearers

What came first? the chicken or the egg? No really.....

A lot of guppies and other livebearers have pigmentation that changes as they age , but there are a few other causes that can darken an eye or cause haemorrhaging. First and most likely is a lack of dietary zinc compunded by the unfitness and vulnerabilty that livebearers suffer as a hereditary weakness inflicted upon them by overbreeding and limited genepools, given increased zinc in the diet it can be corrected.

The other and altogether less pleasant cause aside from all the usual bangs, bites, and incidental bacterial, monogean and protozoan, ailments that can hit a fish ( they usually have other visible symptoms too) are various forms of herpesvirus. Most fish species have their own version of a herpesvirus, and rarely do they transmit to other species, but they will have been unnacounted for long enough to have distributed by fishbreeders and the average LFS. Among livebearers internal haemorrhage of the eye is not an uncommon complication for a fish suffering from a herpesvirus. Rather like in humans, herpesviruses rarelty kill outright, but may cause breeding depression and shortened longevity, low immunity, and im pretty convinced such incidences of infection are on the rise, particularly as regards the ever decreasing quality of captive bred guppies and mollies. Obviously , there is no real cure, and not a great deal to be done.

If you see any other symptoms , let us know.