Hi! I have a 7 inch common goldfish in a 20 gallon tank that has been perfectly cycled for 2 1/2 years. I do weekly 50% water changes and he has been happy and healthy. We went on vacation for five days and left the neighbors in charge of feeding our fish. When we came back home, the tank was in full algae bloom and the fish was lethargic on the bottom of the tank. At that point the nitrates we're out of control but ammonia and nitrites were zero. I did a 50% water change, added freshwater aquarium salt for stress, and used prime conditioner. The nitrates came down a bit, but not much so before I went to bed I did another 50% water change. He started swimming around and looking better. This morning he looked really bad, barely alive, so before I tested the water, I just did a 50% water change to try and save him. He seemed a bit better, but now he's just kind of sitting on the bottom and not moving much at all. I just tested his water again and his nitrates were much lower (10-20) but now his ammonia is 1.0 and is nitrites are between .25 and .50. Ph has been fine. Should I wait it out, or do a 4th water change in less than 24 hours? I don't know what happened while we were out of town but I really don't want to lose this fish. He's become part of the family!