Goldfish turning black?

Question
QUESTION: Hi Chris,

I have a 40 gallon Jewel Aquarium with 2 goldfish - one is red and the other is gold/white in colour.  My tank is up and runnning over 2 years.  My PH is 7.5, ammonia is zero, Nitrite is zero and Nitrate is under 5.  I do weekly water changes of about 30%. I have an internal filter which came with the aquarium and hangs on the side of the aquarium.

Last week the gold/white goldfish appeared to be off colour.  Out of the blue he started lying at the bottom of the aquarium, wasn't eating his food, his fins were clamped and his poop was white and stringy.  I dosed the tank with a Tonic but it didn't seem to make any difference.  I also performed a 30% water change to see if it would perk him up but again no change.  It looked as if he was going to die so as a last resort I performed a salt dip on him (WEdnesday of last week).  I put a galllon of aquarium water into a bowl and dissolved 4 teaspoons of aquarium salt into it and then I placed the goldfish in the water for about 2 minutes.  I then put him back into the aquarium.  On Thursday morning when I came downstairs the goldfish was happily swimming about and was back to his active self.  He starting feeding again and his fins were no longer clamped.  I decided at that stage to dose the tank with an anti-parasite treatment just in case that was what the problem was.  I forgot to mention that I got this gold/white goldfish only about 5 weeks ago.  So I dosed the tank.  On Friday I noticed that the gold/white goldfish was starting to change colour.  He starting dveloping very small black patches here and there around his body, very small black patches.  On Saturday he had more and so on and now he has alot of black on his body and some on the edge of his fins and on his gills.  He is acting normally, is eating normally and his poop is normal too, it's no longer white and stringy but is now thick and short and is the colour of the food he is eating.  He doesn't look as if he is ill with any kind of disease but all the same I am concerned about his change in colour.

My questions is could the salt dip and then the parasite treatment have somehow caused his skin to change colour?  I know when a fish has been injured, when he is actually healing, patches appear which mean he is on the mend.  Could it be this or just a natural colour change?  Just to say to you that I also gave my other red goldfish a salt dip and he was in the tank when I dose it with the parasite treatment but he is fine, still red in colour.

ANSWER: Hi Katie;

It sounds like whatever was wrong is indeed going away. The black areas are probably where the skin was damaged. Usually it's from ammonia burns but it could have been a parasite, fungal or bacterial infection that was eradicated with the medication and the dip. The black areas should heal up and fade away in two or three weeks just fine, they're kind of like "scabs". Just watch to be sure your fish stay well and keep up with weekly 25% water changes so the water is clean while they heal.

Another possible scenario is that the addition of the extra one fish caused a temporary rise in ammonia and the effects are just recently evident. It's possible that you didn't happen to test when it was up. Ammonia and nitrite can drop pretty quickly, within hours, but leave the fish stressed and prone to disease and parasites.

Also, if you test for ammonia using the strips or sticks, you might want to throw out the strips and get a drops or tablets kit. The strips have been very inaccurate in my experience.

The important thing is that they are doing okay now. That's wonderful!

Keep up the good work!

At Your Service;
Chris Robbins

---------- FOLLOW-UP ----------

QUESTION: Thanks for your speedy response Chris.  Hopefully the black is as a result of healing.  This morning there is even more black on him, he looks like somebody doused him in black paint.  By the way, I use the drops to test my ammonia and not the strips and the kit I have is only a few weeks old.  Surely if there had been an ammonia spike with the addition of the new fish, my old fish would have been affected?  Also why could there possibly have been an ammonia spike considering my aquarium is quite big for two goldfish?

Answer
Hi Katie;

The black can continue to appear after the exposure to ammonia is over. It's a sign of healing. It will get better though and fade away.

It is very common after new fish are added for an ammonia spike to occur. The beneficial bacteria that lives in your tank had just enough colonies to control the ammonia your first fish made. Then, add another fish, basically doubling the bio-load (waste, respiration) and the bacteria has to jack up it's population. Thus, an ammonia spike until the bacteria compensates. Unless you test for ammonia once a day, you may not even detect it if it balanced out pretty quickly. Not every fish is affected the same way and not always to the same severity. Just like people. Some of us get sick easily or are affected by things in the air more than others. The newer fish was probably stressed from going to a new home and it can cause weakness for a little while, even in a good environment such as your tank. It's hard to say what he went through before you took him home too, or how strong his genes are. He's lucky you took him home.

Keep up the good work and I hope your little guy gets better very soon...

At Your Service;
Chris Robbins