Been debating posting this, since it's a ways outside the usual subject matter here, but the more appropriate forums I read ended up being entirely unhelpful.
Ok, so long story short, I've got fish, and I have friends. My friends see tanks all over my house with healthy fish and little fry peeking out of broken flower pots, have a pang of guilt for the goldfish they had for three days as a child, and ask me how I do it so they can get a tank. Usually works out quite well - some of the people I got started have done the same with their friends and relatives.
Until this new guy decides he wants a tank. Insufferable know it all, and being one myself, I know I'll regret helping him, but I print up the instructions I keep saved for buying, setup and cycling and tell him I'll help him with stocking when he's followed all of that to the letter.
Two days later he tells me he threw out my "useless shit" and took "professional advice" (high school dropouts reading canned answers off of cards printed in the 70's). Everything's doing fine, the water stabilized on it's own without the procedures I wrote up... So he thinks.
So he buys of all fish discus (for the unfamiliar, discus are one of the most difficult freshwater fish to keep). At $50 each, all four are dead overnight. So he seeks "better professional advice" and stocks with goldfish temporarily. I got a look at the tank, the goldfish have ammonia burns and are showing signs of suffocation (normal for the likely water quality), but nothing that can't be fixed if he takes action.
So I give him some emergency intervention advice, a scolding about how much more extra work he's made for himself, and hope for the best. I also snuck a water sample out and tested it at home, and no surprise the ammonia was through the roof.
Long story short, he doesn't take the advice, fish are dead. He bought a third batch, which died within hours (probably shock or a pH crash). Somehow now it's MY fault. Even though he's claiming I did something to the water, he still won't change it, so his subsequent fish have all died quickly as well.
Anyway, I don't know how to deal with him and nobody else seems to be giving constructive advice:
Other friends: Actually poison his tank.
Other fish keepers: Cram him in a small box full of his own urine so he knows what the fish went through.
So I finally decided that somebody outside both my circle of friends and the hobby might have a perspective that won't end with bizarre pee puns on the front page news.