Well, I was basically hoping that a seasoned veteran, an expert, or someone with tons and tons of reef keeping experience would detail any recent blunders or mistakes that lead to some kind of major problem in their tank. The idea being that even the best aquarists make mistakes and that us

ies aren't alone.
Well, for what it's worth, I'll give it a stab:
I was in Hawaii on vacation and I noticed these cool looking snails, black nerites I think and periwinkle snails in the intertidal zone. So I figured, I'd snag a bunch on the day of our return home and toss 'em in my tank. Yay, more clean up crews!
I go home, acclimated them with a nice slow drip over a couple hours and then introduced them into the tank. It went really well for weeks! I was so happy (but knowing that I probably broke a bunch of fish and wildlife laws... looking back at that I gotta say... bad me!!!!)
But slowly, these new snails were disappearing one by one. I couldn't find their shells. Did they bury themselves? I didn't think these intertidal snails burried themselves.
The numbers got down to near 0 when I started poking around the back of tank. There they were! Stuck to the back of the tank. They had secured themselves back there with their mucus lining and waited for the tide to come back. Most of them were dead

but amazingly enough, some were still alive when I pulled them out. The ones that were still alive were moist and reactive to touch. So I tossed those guys back into the tank.
Bad, bad me for collecting them in the first place. And dumby me for not realizing that intertidal means... um... intertidal.
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Oooh, now here's a really bad one. Top off water. I come back from a week long vacation and I had forgotten to ask the house sitter to top off my tank. So when I got home, 1/4 of the tank's water was gone! So I got some
RO/DI water together and I dumped it in. All of it. All at once. That killed off a clownfish (female of a pair) and a couple of other fish. Like within 10 minutes! It was horrible. I just wasn't thinking!!!!
