Responding to your last two posts.
The cichlids in the photos are African rift lake species. These fish need moderately hard or harder water (the GH which is general or total hardness, primarily a measure of dissolved calcium and magnesium) with a basic pH (pH above 7.0 which is neutral, so up around 8 would be best). Water parameters are critical for fish because of their physiology; water is continually being assimilated by osmosis, entering the bloodstream and internal organs. Each species of freshwater fish has evolved over thousands of years to function best in very specific environmental conditions which includes water parameters as well as the habitat and other species. In the case of hard water fish like these cichlids, they must have these minerals in the water or their metabolism will not function properly. This adds more stress, and stress is the direct cause of about 95% of all fish disease issues.
Rift lake species also have other necessities. They need a fair number of them, not three or four or five, but a tank full. Some writers refer to "overstocking," though that can be misunderstood. But the point is that they are a very unique group of fish with very different needs from any other freshwater group.
In post #16 you write "
Only thing.he suggested that these fish can sustain high on water." I've no idea what this means, perhaps you could explain.
most articles just mention on levels for turtle, ammonia levels nitrates and nitrites, which overall is the same byology for fish from what i undrstand, expcept for some pointers that they require individual and different number.
I know how ammonia, nitrite and nitrate affects fish, but that is because fish are assimilating the water with everything in it, and all three of these are very toxic to fish. Ammonia and nitrite can kill them rapidly, nitrate over time will weaken them significantly and lead to death. I cannot see this being the case with turtles.
Ive seen some youtubers have both cichlids and turtles which im guessing their water chemistry is.more to accomodate the cichlids but they seemed healthy and happy, maybe is that they are adult so they can adapt better not to sure ?
We should never accept anything we see online as factual, accurate, advisable...unless we know first hand the source. Anyone can post videos, anyone can set up a site as "expert," and promote misleading inaccurate information. Know the source, always. There are reliable sites run by ichthyologists and/or very experienced hobbyists whose reputations are established.
Second point here, is that again it is usually impossible to assess impacts externally. We have to rely on the advice of professionals. Fish are very much more difficult to diagnose. Impossible for most of us in many cases. This is the value of research from reliable sources, so we can avoid the errors and have healthy "happy" fish. Take nitrate as an example: ammonia and nitrite kill fish quite rapidly, but nitrate does not; the fish slowly weakens (this is not observable in most cases) until it dies, prematurely; necropsy would usually reveal nothing, but we know that it was the effect of nitrate over time that weakened the fish to the stage where it simply could not carry on with life. Often other diseases take hold because of this weakness, so it is easy to assume it was "X" or "Y" that did the fish in, when in fact it was nitrate. Just one example.
Adaptation is a word bandied about in the hobby but usually misunderstood. A species that has been programmed to function in a very specific environment is not going to "adapt" either rapidly or significantly, depending upon the relevant aspects. These basic needs are in the species DNA and only change over time with evolution of the species. It is also not surprising that many of the species that have been commercially raised for so many years now are showing considerable weakness in the genetic make-up. We do not know better than nature, and it is time we started accepting this fact of life.