My housemate saw this thing crawling along the glass in my Guppy tank adn freaked out, she didn't realise it was dragging an Anubias leaf with it!
I think it's a Caddisfly but it had lots of little legs, rather than 6 big ones like the Caddisfly larvae on the internet.

Anyone have any ideas? Sorry about the pictures, it wouldn't come out for a shot

It must be a cased caddisfly I think. You could be mean and open up its case to have a proper look - it would repair it. It's been very clever to use an Anubias leaf like that.