I asked what they were and was told they were yellow upside down catfishes.

What might they be?
They were really tiny, about 2.5cm and I couldn't really get a good look at the shape of them as they were all together and moving very quickly.
When their "hide" was lifted they scattered in all directions, and not all swam upside down, so I deduced that they are probably not a yellow type of nigriventris, if such a thing exists.
Anyone any ideas what they could be.
Ian