Hah! I got you beat on impulse buying, Scott. Not that this is a good thing, though
Several years ago, we bought this really cool looking 12" fluorescent orange worm-thing. The store didn't have any info on it and when we got back home, we did not or could not (don't remember which) find any info on the net for it. Long story short, it lasted about 5 months. Then one day it died, but we didn't know it. But our large fish sure did. They dropped like flies because of some toxin it released after death
Lost our beloved marine betta along with a few other really great fish.
Now, we don't buy anything exotic, and research the heck out of a new addition before buying. If there is a fish at a lfs that looks cool, we ask to look it up in the books. Just this week, we saw a great looking fish that sort of looked like a moorish idol, but wasn't. Turned out that the fish grows to 13", is very shy and likes to hide in caves most of the time. Thank goodness for research!