It doesn't need to be a massive shock. Just enough to stress the fish.mistergreen wrote:
You're talking about massive contration of salt or the reverse (basically distilled water).. I doubt that was the problem.
This has really got me thinking though.
A fish like a clown loach has an unfortunate journey where it might go through osmotic shock and/or environmental stresses once, twice, or several times from the time it’s fished out from its natural waters, then moved to the exporter, then shipped to the importer, then to the local fish dealer, and then into it’s final destination.
An analogy would be like it’s an earth quake to the fishes body. The initial tremor cracks the structure, the aftershocks weaken the structure to the point of failure. The aftershocks may be days or weeks after the initial shock.
Osmotic shock also weakens the immune system, and that can open the door for deadly bacterial intoxications and/or parasitic infections. Whatever the cause, I can point the blame on that the fish were new. I would expect some problems when getting new fish, especially if there was no quarantine, and if some of the water parameters were not known. IMO, pH and temperature are not nearly as important as knowing the Nitrates, gH, kH, and TDS of the lfs’s bag water, tank water, and source water. Acclimating needs to done slowly nevertheless.
There’s a lot more to acclimating.
The fishes senses need to get accustomed to the waters temperature, ph, it’s lighting, sounds, vibrations, and smells.
The fishes internal organs need to acclimate to the new water chemistry, which are things like gh, kh, tds.
The fish needs to build up tolerances to the new biological environments, that includes micro organisms, bacterial colonies, yeasts, molds, and parasites. Some good, some bad.
The fishes temperament needs to adjust to being in captivity with no place to go, and they must adjust to living in a hierarchy with other fish.
The fish needs to adapt to it’s physical surroundings. To find a safe place to rest, to not get sucked up by filters, to not keep running into the glass, to know where to get food.
It’s a lot for a young fish to take all in at once. It’s a lot for a new fish owner to take all in at once also.
I think about being in the fishes “shoes”. I imagine being dropped off in the middle of a rainforest in Borneo, with nothing but the clothes on my back. I think I would fall ill and die after a few weeks.
It's time for lunch and for me to zip it. It was nice chatting here the last few days, but I've got some work that I must do now.
Anyways, I hope this problem resolves itself. I wish good luck to the fish Shazam.
I'm very frightened for the fish. It's at least a week till the new shipment of medication arrives and who knows who could die next in that time. 
I'm very sad because I love these fish very much as well and both of us are completely stumped as to what we could do.
