I woke up this morning and I couldn't see Audi anywhere after searching hard I looked in one of the two caves and he was lying on his side. He's now passed away and I'm blaming myself for this.
People might just say it's a fish but im traumatised about his death. I should have done things quicker and diagnosed the right problem first. I'm now going to re-home Quattro aswell because I can't help but keep thinking the position of Audi in the tank this morning :( Thanks everyone for your help it was much appreciated.
Sparko, if you're reading this, you need to get your fish to a vet. He has a very serious bacterial infection. Try Melafix in the meantime and try to work out how/why the infection started (was there a problem with the water?). Perhaps start your own thread.