Sorry, I thought that the course of action would have been obvious, I guess not.
In the case of any kind of potential toxin the thing to do would be to either immediately remove the fish affected from that potential toxin, or attempt to remove as much of the toxin from your system as possible. A large water change without the garden hose would have been one option, another would have been to run some carbon through your system ASAP. Not knowing for certain whether the issue was your tap water, or the garden hose, I would have personally gone with some high quality activated carbon, at least for a starter.
All fish react differently to various toxins. What might be safe for one fish, could prove deadly to another, sometimes even within the same species. So no real surprise that only your ray reacted to the water change, and as previously stated seeing as the only thing that was out of the norm was your use of the garden hose that would be the best bet as to what caused the problem.
In the case of any kind of potential toxin the thing to do would be to either immediately remove the fish affected from that potential toxin, or attempt to remove as much of the toxin from your system as possible. A large water change without the garden hose would have been one option, another would have been to run some carbon through your system ASAP. Not knowing for certain whether the issue was your tap water, or the garden hose, I would have personally gone with some high quality activated carbon, at least for a starter.
All fish react differently to various toxins. What might be safe for one fish, could prove deadly to another, sometimes even within the same species. So no real surprise that only your ray reacted to the water change, and as previously stated seeing as the only thing that was out of the norm was your use of the garden hose that would be the best bet as to what caused the problem.
