sick fancy goldfish

Question
Hi Shorty.
I am hoping you are able to help me as I am desperate and cant stop crying.  It sounds so silly to be so attached to a goldfish.  We have a 50 gallon tank with 6 fish all a type of goldfish, but the one with issues is a fancy goldfish.  Several weeks ago he began developing two little black spots on the top to sides of his head.  He seemed fine, no problems and I just watched it.  So last night when we came home those two spots have fallen off.  They kinda left like a scab if you will.  About 9am this morning he began getting very lethargic and turning upside down periodicallly.  Now it is at the point where he is just hanging out on the bottom of the tank upside down just listless.  Its breaking my heart, as he is a silly fish, and gets super excited when I even talk to him.  I have done tons of research today and went to the pet store and got melafix for the tank.  (unsure of spelling sorry) also some electrolytes.  I have been feeding them all flakes which is research found out about the bladder issues.  So I bought him sinking pellets.  However, he is not eating and I am holding food anyways in case it is "constipation".  In addition when my husband got home from work this afternoon he did a 50% water change.  Any other suggestions would be great to what we should do.  I really, really dont want to loose him!!  Please help however you can.  Thank you for your time.
Holly

Answer
Hi Holly,

I pulled your question out of the pool.

Have you tested your water for ammonia, nitrites and nitrates?  99% if the time anytime your fish has an ailment it's directly related to the water quality results of these tests.  You should always have 0 ammonia, 0 nitrites and 5-20 ppm nitrates.

What kind of filtration do you have?  A 50 gallon tank with 6 goldfish is just slightly overstocked so I would make sure to run a 100+ gallon filter and do weekly 25% water changes and gravel cleanings to keep up with the awesome bioload that these fish produce.

Melafix is for a very mild bacterial infection and what is probably of more use at this point is aquarium salt.  Try 1 tsp. per 5 gallons of aqua salt and this will reduce stress.

Good luck : ) April M.