The no flash rules make getting good pictures hard but i did manage to snap a few of the clown loaches they had.
I would estimate that they were 8-10" in size.
Oh that i could afford the set-up they were in:
If anyone is interested in browsing through the rest of my snaps from that day they can be found in the following album:
http://picasaweb.google.com/dienyddio/LondonAquarium
No snaps of the stone loaches though )-: