Hey there - Urgent Black Moore Needs Help

Question
Hey there, i am from New Zealand and i have previously been on here and talked to a lovely lady by the name of Renee unfortunately she is no longer on here so I'm seeking help from other experts :)

I have a Black moore in a 5 litre tank which i was told had been right by the pet shop, but Renee told me that they had wrongly informed me and he needed at least a 30gallon tank with a 50gallon filter which i also do not have, I had first contacted her as My black moore had begun growing a sort of fluffy mould on him. This happened after another fish in the same tank had died from floating, but i immediately removed the dead fish and cleaned out the tank as not to effect the Black moore.
She had told me to salt his water which i had done and the fungus had gone away, i change his water almost everyday and he has been fine, i checked his tank today and he had mould on him again but almost twice as bad, My mother has been meaning to buy me a larger tank and filter recently but unfortunately we do not have the spare money at the moment. He also sits in the water looking depressed and floats at the top but not upside down.

I hate seeing him being put through pain, I don't know what to do anymore, Please help!!!!

Answer
Tess,

I have to agree with Renee 100%. That tank is way too small for ANY fish. Goldfish are huge waste producers and is one reason why they need such a large tank. Since they do over produce waste it is always a good idea to buy a filter that is larger than the tank. What you can do is go to any store and buy a large plastic container. A tank can be anything that holds water. The plastic containers are a lot cheaper than an aquarium. If you do not get the fish out of that small tank it will die, and soon. If your fish is hanging out at the top of the tank, that is a sign that there is not enough oxygen in the water. Add an air stone and that will help. If you need any more help, don't hesitate to ask.