Blackmoor appears to have popeye
We're got a Blackmoors goldfish that we noticed was lethargic recently so we kept an eye on him/her. After about a week we noticed that he had what looks to be popeye in his left eye. We started treatment immediately, 80% water change, doubled the quarium salt we normally add (around three table spoons this time around) and begun treatment with API Furan 2. After a week or so the treatment had made no difference so we switched out about 80% of the water again added melafix and pimifix along with the same amout of salt. After another week with no change we had to stop treatment due to the fish being at the top of the tank gasping for air (immediately changed out another 80% of the water). After this we have stopped treatments but kept up the salt treatment. We fear the Blackmoor will lose his eye as it has not come down at all and is still protruding a long way. None of the other fish have any signs of popeys and the Blackmoors isn't showing any signs of being off his food and they are all still active.
It is a 90litre tank, it has 1 Blackmoor, 1 celestial and 1 fan tail.
We live in New Zealand and erthromycin is not available to us.
Is there anything else we can do to help him/her?
Thank you for any advice offered