disaster

I got some rocks from outside and soaked them for about 10 minutes in a little bit of diluted antiseptic and then scribed them repeatedly to remove it from them. I then put them in my brand new 125 l tank and by the morning it killed my fish and leached the antiseptic into the water. I then...

I have been keeping fish for a long time, but I have NEVER had something like this happen! I've no clue what could have gone wrong.... Here's the situation: I've been away from home for about a week, the care of my tank was entrusted to a friend and fellow fish mom during that time, due to my...