Harlequins and neon

Cleaned Emily's fish tank today and thought Id try and get a photo of some of them; it was very tricky, they never stay still, photobomb all the time and are clearly very active when I'm near the tank (always hopeful of a feed) so I had many very blurred shots. I will have to experiment more with this, though a tripod and shutter release was very helpful. Just a crop on this photo, nothing else. I'd be very grateful of any tips on photographing fish in tanks.