Black pulled in fins

Question
Hi i have a white goldfish and hes getting black on the tips of his fins. Along with that the fish fins are always pulled in against the sides of his body. The top and two side fins, Making it look as if he doesnt even have any. So he's basically using only his back fin to swim, and struggling. Please help, thank you.
Tank Info:
15 gallon tank, not new,68 to 73 water temp.
With 3 other goldfish and a loach.  

Answer
Good evening Andrea, thank you for your question.

Clamped fins are a symptom of environmental disease, they often accompany an ich outbreak. Black fins usually signal ammonia presence in your tank. These symptoms are due to water quality issues, and water quality issues are due to the high bio-load in your tank. Three goldfish is really too many, there should only be one goldfish in a tank that size. One goldfish per 20 gallons is ideal. What you will have to do is bring up the water quality best as you can:

First, vacuum the gravel. Goldfish produce lots of waste, and uneaten food and wastes will sink to the bottom, fouling your tank. This is why the gravel must be vacuumed once every two weeks, the ideal regimen is 50% of the gravel once a week in an alternating pattern.

Next, do a large water change, 50% should do it, with declorinated tap water. The new water should perk your goldfish up a bit. I would add two teaspoons of aquarium salt to your tank as well. Add it to the water change water and shake it up so that it will dissolve - it is best not to pour aquarium salt directly into the tank. Keep in mind that aquarium salt does not evaporate, it dissolves and becomes "one" with the water, so don't keep adding more and more!

I am not sure what sort of loach you have - a weather loach, perhaps? Hopefully not a loach that requires tropical temperatures. Loaches can be fussy about water quality, clown loaches are considered "ich magnets" for this reason - do service your filter often, rinsing or replacing the media weekly, and perform two 25% water changes per week.

See if a step-up in maintenance does not rid you of your problems for the time being. Goldfish are frequently overfed due to their begging habits - they really only need two light feedings a day, and would relish a healthful treat of pond plants such as elodea and anacharis.

When you test your water, you should have no detectable ammonia or nitrite, and under 20 ppm of nitrate. Higher levels than these will cause health problems, and I suspect it will be difficult for you to maintain these levels in a system and stocking of your size. Do look into a bigger sized system for your goldfish for their long term health and vitality - they can live for longer than a decade!

Good luck to you,
Nicole