Originally Posted by calfishguy
I myself won't call 80° an extreme difference from 78 but that's just me. I also checked three websites and two of my books and I believe 78 is fine for rams. Just to confirm something though do you know if there are references for the info in the fish profiles.
My apology for not seeing this and responding sooner, but better late than never when it comes to information.
The difference between 78 and 80 F is very significant for a fish. We humans cannot assess temperature based upon our experiences because being mammals our body internally controls our temperature so that our physiological functions continue. Fish do not have this option. Another factor is constancy; an artificially heated aquarium is far removed from the environment that fish are designed for with respect to their physiology. If you are interested, you can read a bit more about how these external factors affect fish in my article on stress: http://www.tropicalfishkeeping.com/f...um-fish-98852/
I`ll comment on the source for the profile data momentarily; but the given temperature range for each species is the range in which the species will generally manage with respect to the internal physiological processes. As a permanent temperature, mid-range is where it should be; this is the temperature at which the internal processes will function without the fish having to expend additional energy. The upper and lower limits of each range are temporary situations only, meaning that the fish will manage
at these extremes but should not be maintained at them continually. When the fish is forced into using additional energy just to carry out the homeostasis, the fish is literally wearing itself out faster. This can weaken the fish, lessen its immune system response, and almost inevitably lead to a shorter-than-normal lifespan. The linked article explains this.
To the profiles: I authored most of the freshwater profiles. I use an extensive range of reliable data sources, the sources of which are ichthyologists, biologists and acknowledged authorities. When it comes to differing data, I indicate this; but otherwise, you can assume that the data is that held by all.
This does not mean that you will not find differing views on the internet. While the internet is an incredible resource tool, the fact remains that anyone with the money can set up a website and promote this or that, with no scientific scrutiny. The reliability of the source is critical. Taking the temperature for the common ram, Mikrogeophagus ramirezi, this should never fall below 80F, and 82F is the preferred temperature. This species has a lifespan of 4 years, but it will rarely if ever reach that at lower temperatures.
Hope this has answered your questions, but feel free to ask further.