I recently set up my fish tank, had the water tested and my fish are rapidly dyeing. What can I do about this?

What was the results of the test? Perhaps you placed the fish in the tank too early.

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Update: Goldfish are pretty damn hardy. So maybe there's something in the tank that's toxic. Is everything in the tank from the fish store? Maybe you put something in there that doesn't belong?

It could also just be that you got a bad batch of fish. That happens sometimes.

What size is your tank? How many fish are in it and what size are they? Are they gulping air at the surface of the water or sitting on the bottom or both? I moved into a house years ago that had copper pipes and acidic water that was less than 6.0 on the pH scale. My fish were poisoned by this even though it was well water. If you can go to Youtube see O' Fishely Channel, or Father Fish and we will be happy to help as you progress with your fish. Don't give up, there are answers to every problem.

What you need to do is read up on the subject and look at the equipment and plan out your hobby before you do anything else.  If you goldfish died as you have described, the reason has to be you.  Whatever you did, whatever information you disregarded, whatever assumption you made, whatever you don't know, etc.  For example, it could be that it is not the tank or the water, but is that you bought the goldfish in a little plastic bag and left it in the car for 2 days while you played video games.   Then you mom reminded you of the fish, so you got them and dumped them in the tank.  The people at the store told you the water had to be so-so and sold you a test kit.  So, you tested the water and it is OK.  Now you are confused because you did all that you know.  So, what could be wrong?

get gud                   

How recently did you set up the tank? Did you get your water tested before or after you cycled it? How did you cycle your tank? If all you did was let the filter run for 3 or 4 days, then you did not cycle the tank. And, of course, your water test is going to have 0 ppm ammonia and nitrite because you didn't add any. But, after you add fish to the tank, they'll start pooping in the water, adding ammonia, causing water quality to deteriorate. A healthy tank should have 0 ppm ammonia, and nitrite but there SHOULD be a nitrate reading. It means you have a colony of beneficial bacteria that converts toxic ammonia (from fish waste) into less toxic nitrate.

How long did you cycle your tank before you added the fish? Did you retest after you started having issues? What parameters did you test, and what were the specific results? What's the temperature in the tank? Source of the water?  Size of tank and number, size, and type of goldfish? 

What type of fish and what did the water tests say?  Did you use tap water and if so did you dechlorinate the water.