Black moor illness

Question
Hello, I'd like some advice on my black moor please.
In early March I was given a 30-40 litre tank and bought my son a canary and gold fish.  A week or two later I added a black moor and gold fan tail.  Since then I done a bit of revision and realise the tank is way too small.  
As we were saving for a new tank the gold fan tail became unwell, he started floating side ways and just basically gave up.  We bought a bigger tank the same day and prepared it, meanwhile I added aquarium salts and swimbladder treatment, unfortunately he died. I did a 25% water change as soon as I removed him.  
I added the 3 remaining fish to the new 120ltr tank after settling it for a week, adding filter start and aquarium salts and also two new baby orandas.  
One of the orandas started picking on the moor nipping at him (the same fish died after 6 days when he got stuck in a artificial plant).  I noticed one scale on the moor's side is very enlarged and see through at the tip and is white and fuzzy closer to his body.  Also his scales all over are quite raised.  He's been like this for 12 days or so now and I'm unsure what to do.  I've searched the net but don't want to add treatment till I know exactly what it is!!!
Your comments and help would be greatly appreciated.
Thank you for you help x

Answer
Hi Katy,
There are a couple things wrong with your fish. It is not my area of expertise with sick fish however I will try to help you with the research and the experience I have.  The white fuzzy stuff you are seeing sounds like fungus to me and can be treated with Maracyn or Maracyn Plus.  Also, you said the scales are raised.  Every time you see a fish getting bloated or larger with scales being raised, you have to take action immediately because it sounds just like symptoms of Dropsy which is fatal to the fish.  Give him Anti-bacteria medicated fish food and also, add aquarium salt to the water.  The reason for the salt is to reduce the edema (liquid overload), that is causing the bloating.  The salt will cause osmosis to remove some of the water from the fish to reduce the swelling.  
Hope I helped,
-Matt-