In this thread post your most idiotic reefing mistake

[Madreefer]

Originally Posted by Magickiwi

My biggest mistake wasn't really my mistake exactly. I simply listened to the dude at the LFS when he said a green brittle star was reef safe. Well by reef safe he meant it wouldn't eat corals, what I THOUGHT he meant was that it would co-exist without harming anything in my tank (Normally what is meant). Several fish later I finally caught the bastard in the act and then had to take apart large portions of my rock work to get the big sucker out.

Lesson learned: People at the LFS aren't necessarily speaking in the same context as you so do your own research and trust nothing unless you've verified it with a valued source.

I think this is the biggest mistake we all make especially when starting out. It took me a couple of years to wise up and stop listening to guys at LFS

[Parker]

Don't set a 400w fixture on your center brace.

[trilinearmipmap]

OK mine looks like the 3rd worst mistake after the cracked centre brace and the light fixture dumped in the tank. Now I don't feel quite so stupid.

[monocus]

putting a helfrichi gobie in my tank.my male bird wrasse had a $140 lunch in less than 10 seconds

[Coral Hoarder]

O ya I forgot one I put my 3 250 watt mh fixtures on the glass had a fish splash the glass and broke

[kengeroo]

got really lazy one day,,, added salt directly to my tank,,, straight into a clam.....

[shrimp]

Might as well post mine.
Years ago, I was doing a tank move and fished out all my fish to a 5 gallon pail. As the move was taking longer than expected, after some time I figured that the water must have cooled off too much, so I decided to place a heater to warm up the water a bit.
Even though I had the thermostat set to turn off when the water would heat up to the desired temperature, I "boiled" all my fish as I did not have a small circulating pump in the bucket.
It still pains me to think about those poor fish that day, even though it happened so many years ago