05-28-2012, 12:29 AM
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Originally Posted by Olympia
Temperature fluctuations frequently cause poor embryo survival, low hatch rates, reduced growth rate, increase in deformities or larval disease, in both blue eyes and rainbows (though I suspect blue eyes to be more sensitive?).
It's estimated that in the wild, larval rainbowfish mortality rates are as high as 99.99%, so I guess you're right and their environment does fluctuate a lot. I know their particular habitats are in general crazy, most fish rarely reach a year past adulthood, but they breed fast and often to make up for this.
Ever gone swimming in a lake at night? It feels extremely warm compared to the air temperature, doesn't it?
Shallow water species are probably much more tolerant of changes, as well as fish that live in places where natural flooding/droughts occur, but water in general is a great insulator and holds heat very well.
Both shallow and deep water species have pretty good tolerance for change. If you have ever gone diving in a lake there is always a thermocline somewhere which is a ~10 degree or so temp drop over the course of only a few feet.