Never heard this happen

[Raedwulf]

I have a 90G tank with a variety of fish, primarily Rainbows. I keep a number of Ottos to help out with algae. I had begun to wonder why I could never find more than 2, I was sure I had at least five.
Today my eye caught some three-line Rainbows and decided to get 5 more Ottos.
I performed the standard climatisation, but temporarily forgot about feeding before releasing the new fish, but remembered immediately after.
When I looked in the tank to check on the new guys, I found one of my larger Yellow Rainbows with a tail sticking out of his mouth.
This is the first time I had ever seen my Rainbows attack any other tank mate, much less eat them. I even keep Threadfins, smaller than an Otto.

[Gisela]

I guess you should have fed them first, also it helps to turn of the lights.

[skullduggery1]

I guess you should have fed them first, also it helps to turn of the lights.
apparently otto's are like potato chips.

[Lady Hobbs]

I have one lonely otto in my rainbow tank for 3 years now because I haven't been able to find more. But I will not put neons in a tank with them because I've been told they "will" eat small fish. They have a big mouth but a narrow throat and they will get it down.

Otto's are very fast tho. Surprised the rainbow was able to catch him.

[Gisela]

Well, I guess I should phrase it different. I didn't mean he gets more otos, just when he did put them in maybe it would have helped feeding them first and turn the lights out. I love otos and own them in two of my tanks, too.