Hi, I hope someone can help! I got my fish tank 5 months ago and have a 60litre tank. I have 3 guppies, 2 neon tetras, 3 mollies, 1 plec, 2 cory cats and 'goldilocks'- the golden loach. The tank has been going fine up until recently but then my fighter fish was attacked, i then got guppies and...