Well, good intentions are awesome.. but sometimes they cause your tank to crash.
I am a big fan of the quarantine tank. I keep an extra foam in my tanks in case I ever do make a random fish purchase so that I can just pop it into my little QT. However, my boyfriend has only recently gotten into fish.. and he's a lot less nerdy about it. He goofed and bought 6 giant gold danio's for his 35g octagon tank. I really kind of lectured him(I know, I'm a buzzkill), that they really needed a longer footprint because they were very active swimmers. He couldn't take them back to the store so I ended up with them in my 60g. I probably wouldn't have bought them but they are very active and peaceful and they seem happy to zip around, so they grew on me.
Well, a few weeks go by and everything was fine.. I had a few days off from work and was going to take a foray into live plants. I had plans on one of the days and was out pretty much the entirety of it. I come home and meander over to feed my fishes.. when I spy about 8 very sickly looking cardinals that I know were not there when I went to work.
Don't get me wrong. I LOVE cardinals and have had really good success with them, but I always QT.. turns out my boyfriend decided to surprise me and added them when I was out. I kind of freaked and removed them and added them to the QT hoping that maybe it wasn't too late.
It was.

They must have been the most stressed out ich infected fish I have ever witnessed. One by one they died off, excluding one little guy who is apparently made of a sterner stuff.
This all caused something of a domino effect and my german blue rams as well as a large group of my preexisting cardinals and neons died off overnight. Does it usually happen that fast?!
My parameters were fine, not even any ammonia was present from the newly added fishes. The rest all just seemed to keel over.
I've left everything alone and kept a really close eye on water parameters and everyone seems fine. I have a german blue pair sitting in my QT waiting it out.. but I'm still worried about adding them!
I think I'm too paranoid sometimes, but I love my fishes.