I totally inderstand your frustration. I believe I would be livid as well. YET, if it wasn't done out of malice and it was an honest mistake, maybe you should forgive them. I would expect my system to be replaced. Look at it this way, ehat if one of your children did something thar killed all your fish, would you forgive them? Well, again if it wasn't done out of malice, they are your parents so forgiveness is important. Not sure how religious you are yet we are supposed to forgive others to be forgive ourselves. Everyone makes mistakes especially in this hobby. Unfortunately we are trying to keep an ecosystem in these glass cages for our own enjoyment, it's very sensitive when coming to water quality as you know, im sure your parents thought they were doing the right thing. Forgiveness is hard sometimes yet it is necessary not to hold grudges. The worse thing is to be vengeful. As a parent myself, if I had done something like they did and I didn't know any better I'd replace my child's entire system and probably give them an upgrade in the process.