Cheers Simon, I've tried taking a pic to post on here but to be honest, it's hard to see the slime as it's very thin. I've put it back in the tank and I'll see how it goes. I'm expecting my plants any time now and I was worried it might spread to them but from what you've said, it shouldn't be a problem.
On another matter, my TDS meter has arrived this morning and I've tried it but can't get a reading on either of my tanks, that's the Cichlid tank that's ran for years, and the shrimp tank. The reading for both is 000, having never used one, can this be right? I'd have thought there would be some solids even in the purest of water.