Have just lifted up the bath mat (suckery bottomed one) in dd's bathroom and the cleaner has obviously not been picking it up and scrubbing and it is all covered in skanky greyish black stuff that has stained the rubber. Don't want to chuck it out as it is fun, has a load of goldfish on it disappearing down a plug hole and she loves it (plus cost £25!)
How can I clean the skank off it?