Goldfish Fin Rot?

I recently got a oranda goldfish to put in my 30 gallon aquarium. I cycled the tank for about a month before putting in the goldfish and it has a heater and filter. The temperature is currently at 80 degrees F. I've been trying to bring down the temperature a bit because I know that goldfish do better in the 70's range. The filter isn't great, it's meant for a 30 gallon tank. So I take out about 30% of the water during water changes (which I do once or twice a week). The oranda is the only fish in the tank so far.
These are the parameters:
Ammonia: 0
Nitrite: 0
Nitrate: 45 ppm
pH: 6.9

I alternate feeding her spinach/other greens and goldfish pellets twice a day. I've had her for less than a month and her fins were fine when I got her. It's been about a week since I've noticed her fins and tail fin becoming slightly ragged. Three days ago, I went out and got Melafix. I followed the dosing instructions and it is now her third day on Melafix. The tank has become kind of cloudy and it looks like her fins have gotten a little worse. She seems less active than before but she still devours her food and swims up when someone approaches the tank. I'm worried because I really love her and would be absolutely broken-hearted if she died. I'm not even completely sure if it is fin rot, much less if its bacterial or fungal. Can someone please, please help me and tell me what to do?

 

I recently got a oranda goldfish to put in my 30 gallon aquarium. I cycled the tank for about a month before putting in the goldfish and it has a heater and filter. The temperature is currently at 80 degrees F. I've been trying to bring down the temperature a bit because I know that goldfish do better in the 70's range. The filter isn't great, it's meant for a 30 gallon tank. So I take out about 30% of the water during water changes (which I do once or twice a week). The oranda is the only fish in the tank so far.
These are the parameters:
Ammonia: 0
Nitrite: 0
Nitrate: 45 ppm
pH: 6.9

I alternate feeding her spinach/other greens and goldfish pellets twice a day. I've had her for less than a month and her fins were fine when I got her. It's been about a week since I've noticed her fins and tail fin becoming slightly ragged. Three days ago, I went out and got Melafix. I followed the dosing instructions and it is now her third day on Melafix. The tank has become kind of cloudy and it looks like her fins have gotten a little worse. She seems less active than before but she still devours her food and swims up when someone approaches the tank. I'm worried because I really love her and would be absolutely broken-hearted if she died. I'm not even completely sure if it is fin rot, much less if its bacterial or fungal. Can someone please, please help me and tell me what to do?
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I wouldn't use melafix because I have heard it takes oxygen out of the water. Try to keep those nitrates lower. I'm also not sure about the greens in her diet...

 

I've stopped using Melafix after 3 days. The nitrates are now much lower after a 50% water change. We're going out to get aquarium salt tomorrow. Would that help? If it would, how much should I put in? Would it have any negative effects/ can it kill the fish???

 

I've stopped using Melafix after 3 days. The nitrates are now much lower after a 50% water change. We're going out to get aquarium salt tomorrow. Would that help? If it would, how much should I put in? Would it have any negative effects/ can it kill the fish???

I think that would help. For dosing I would ask the people at your LFS (unless its a chain). I pretty sure that goldfish can survive some salt with no injury.

 

Do a half cup pet ten gallons, make sure to dissolve it completely beforehand in warm tank water. You can also do a hydrogen peroxide swipe on the affected areas. To do a hydrogen peroxide swipe:
1: Wash your hands well and get all the soap off. Just let the water run over them after you've scrubbed well. Move fish to a Tupperware with some tank water, just so you can work easier basically.
2: Get a cotton ball or q-tip and soak it with hydrogen peroxide.
3: Gently lift fish so the affected areas are exposed, and gently swipe the hydrogen peroxide soaked cotton ball or q-tip across affected areas.
4: Return fish to tank.