My friend has a goldfish bowl and she filled it up with water. I went to her house to see how it was looking and we noticed a small fish like creature!   So we asked her mum what it was and she didn't have a clue. We tried to get it out, but it was too quick!

It was brown and looked slimy, it was quite small, about 1 inch. She has had the tank set up with water in for 3 weeks, in her kitchen. It had a weird shield like shape to it, but it was quite long.     

What is it? What should we do?

       PLEASE HELP!!!!!!