Ammonia and Nitrite Spikes

Ammonia and nitrite spikes require immediate action. Regardless of whatever action led to the problem, the steps to take to remedy the situation are the same. The most common causes are upsetting the bacteria bed by cleaning the bio filter. Another is having an inadequate bio filter, either not enough of the right media or adding fish before the filter bacteria are established.
You have to take immediate action as time is the enemy here.
The first step is to acquire some aquarium salt ( Kosher salt from the grocery) and some Prime water conditioner. If you already use Prime fine, if not, get some. You also need some high quality carbon, (not charcoal, not a resin or ammo chips, just carbon, and a filter bag). If you already have carbon or a resin type media in your filter remove it and discard the media. That includes softening pillows, which is a resin.
Any deviation on the recommended products could affect your success. Especially important is to not get stress coat, which coats and plugs your bio media and builds up on the glass, providing a breeding ground for bacteria.
TRUE bottled bacteria is refrigerated and rather expensive and most stores do not carry it. You do not want to use cycle or one of the many products kept on the shelf at room temperature.
You need to do a 30% water change. Add the Prime to the aquarium before filling it. After filling it, add the salt, one tablespoon per ten gallons. Fill the filter bag with the carbon and rinse well. Place the bag in your filter. Note: Do not remove or disturb any bio media you have in the filter. If you cannot add the carbon to your existing filter, a cheap little hang on filter from Wal-Mart or a discount pet shop would work for the carbon. It just needs to move water thru the carbon.
The fish will not have an appetite. Do not feed them during this critical time.
Daily change 30% of the water, using ample amounts of Prime. Replace only the amount of salt removed – 1 teaspoon per ten gallons. If you see the fish at the surface gasping, change 30 % twice a day. After several days the tank should stabilize. Elevated levels of nitrates indicate the bio filter is function again.
The salt should be discontinued when the tank is stabilized. The carbon should remain in the filter for 3 days after the tank stabilizes. Stabilized means the fish swim naturally and water parameters are right. If nitrites were high and have normalized, the tank is stable.
If the fish are eating, feed once a day only with frozen bloodworms very lightly for a few days.
Normally salt and carbon are not used in the discus aquarium, except for specific purposes. You should never attempt an extremely large water change as it will shock the fish. Breeders doing huge changes on tiny fry have adapted the fish to that and use specialized water.