I'm aware that this may be a slightly controversial topic, and I'm trying to get some opinions.
It can sometimes be confusing when the information across several sites is slightly different and I've been researching information on the internet regarding keeping fish in harder water. The conclusions that I have come to are that the water parameters stated are related to their natural environments, and that farmed fish for the aquatics trade can sometimes be more tolerant of wider parameters than those of wild fish. Some sites stated that a problem with harder water is that the fish won't breed.
I have hard/very hard water of 17dH German, and try to only purchase fish suitable for my water. However, I already own a bristlenose plec and a blue-eyed ancistrus, which usually have an upper range of 15dH.
I spoke to some staff at a LFS today and they agreed that farmed fish can be more tolerant of harder water, and that they use tap water for most of their tanks, with the exceptions of things like apistogramma where they mix tap and RO. I am also aware that fish are only at the aquatics store temprorarily, rather than being exposed to harder water for their entire life, which I'm sure is quite different. They also said that they keep fish at home in the same conditions.
So, my question is basically how hard is too hard?
Is it acceptable to keep fish that are tolerant of up to 15dH in the wild, but are farmed for the industry, in water that is 17dH?
Is is acceptable to keep fish that are tolerant of lower levels (e.g. down to 12dH) as long as they have been bred for the industry and have been kept in harder water?
I am prepared for a rousing chorus of "Donna, don't be so irresponsible as to keep fish outside their stated range just because you really like them and want to keep them", or similar, but would prefer for any "talking to" not to be too much harsher than that, if possible.
Thanks.