Black markings on goldfish

Question
We recently won a goldfish from a local fair. We've had it for about 5 weeks now and have a goldfish bowl with gravel. We use purifying drops which recommend changing the water 1-2 weeks. We have found that within about 3-5 days the water is so cloudy despite using a net to get rid of old food etc. Since getting the fish it's developed black markings on it's tail, today we've notice black marks around one of it's eyes.  Does this mean the fish is ill or do they usually change colour?

Answer
Hi Mandy,
He is either developing color (which I might say probably not depending upon his current coloration) or these are ammonia burns. This would be highly likely due to the polluted environment a fish bowl always guarantees. The best thing you could do for him is to move him into an inexpensive 10-gallon tank with a power filter -- while not a home for life it will help drastically. In a fish tank, special bacteria can develop (that live on surfaces) to take care of the ammonia and convert it to harmless 'nitrate' and you keep nitrate in check easily by doing regular partial water changes.

In a bowl, water changes are often very stressful and due to such a small volume of water, even with daily water changes goldfish just produce far too much ammonia and it becomes highly concentrated in a matter of a few days.

Ammonia burns will heal over time. But the cause must be fixed.

In the meantime you can use water conditioners that neutralize some of the ammonia like Amquel+ or Prime. Ammolock is also good.

I hope all goes well and best of luck!
Karen~