Look what I just found!

[YoureMyWifeNowDave]

hope this works

So what on earth do we do now?

How cute! A guppy? If he's got plenty of hiding spaces then he'll be fine. If not, you could put him in a breeding net or punch a few holes in an icecream tub and float that in the tank until he's big enough to not get eaten.

Just watch out he doesn't get eaten by the other fish. You may need to get a floating tank to protect him until he is too big to be breakfast! Congratulations fish mummy!

I think he is a black molly we are going to try and catch him later and put him in a chinese takeaway tub floated in the tank. At the moment he is lurking round the back of the filter with the plecs

We caught him - he's in a net wedged at the top of the tank and I'm going to get a proper breeding net for him tomorrow