I have a Canon 400D and I have been trying to take pictures of my fish in my aquarium through the glass…?

…but no matter how many times I catch the fish in focus, the picture still comes out blurred. I turn off all the lights in the room so I don’t get a reflection of anything on the glass then I get really close to the fish from the outside and focus. I’m using the kit lens and the fish looks really good when I’m looking at it through the viewfinder…but when I take the actual picture, the shutter is still slow so I only catch a blur from the fish. I’m currently set at 1/10 F5.6.

Please help.