Thing One, Thing Two, and Five Rainbows - Swimming Together

Thing One and Thing Two are Yo-Yo loaches. They like to swim EVERYWHERE with the rainbows, and loaches swimming with rainbows? If you have loaches, do they swim with your fish? It's weird that they swim with something that is not their type, I know people do, but one type of fish swimming with a different type of fish? It's crazy! You should just see them doing that!