Well it happened, I lost a fish.
After 2 months, my Niger decided to eat one of my cleaner wrasses. The funny thing is that as he still had his head in his mouth, the other cleaner wrasse was still cleaning the Niger.
My fiance and I were watching the fish as we usual do and we noticed that one cleaner wrasse was missing. I saw him hiding in a barnacle and then I guess he felt safe, swam out and out of nowhere, the nasty NIger had him.
I am going to get a 75 gallon this weekend to put my Niger and undualtes in. They will have the whole tank to themselves.