Dying fish please help me save it

[tulipluv17]

My fish is suffering and I don't know what to do anymore. Please help me. Everything started when we saw a hole on the head and it had something white inside. It didn't seem to bother it but we were concerned. We have a 55 gallon tank and the goldfish is the only survivor the other fish died months ago. We check the water levels after doing a water change and we had a little nitrate and ammonia. We probably had more before the water change. We used Aquein water conditioner and cycle after the water change. We started the fish on a natural treatment for parasites called Herbtana. After the 10 day treatment the fish got a 50% water change I know it sounds like a lot but we've always done that and the fish is like seven years old. On the same day of the water change, The fish started to develop black spots on its body, it also started to get a cloudy eye and it started Spending more time on the floor. It's been like this for several days now and it barely gasps for air. It finds it hard to swim and it's lopsided most of the time on the floor of the tank. I went out and got it another treatment that is also 100% natural for bacterial disease its called Artemiss. We started the treatment last night. It is another 10 day treatment we removed the carbon from the two filters the tank has and the fish is still alive but it seems to be suffering so much I don't know what else to do please I'm very frustrated. I've been to 2 pet stores and nobody knows what's wrong.

 

[54seaweed]

have you checked your parameters black spots can appear if high ammonia is present
/black-smudge-black-spot-goldfish/

another article about hole in head
/goldfish-hole-head/