RO water would have no ammonia. It also has nothing else. You need to mineralize the water. I suspect your ammonia is a false reading.

I would get a 40# bag of crushed coral and add it to the fish tank. The water will go white for a couple of days then clear.

I would NOT use goldfish. They carry disease and you don't want that. If the perch are not too dear, go straight to them and add the aquarium mulm at the same time. Get the filter gook, not the water.