Extremely High Nitrites

Question
I bought a 20 gallon tank about 4 weeks ago with a 30 gallon AquaClear filter, 18' bubble bar with a pump, gravel, and a water conditioner. I started out with 5 fish: 1 medium sized plecostomus, 1 iridescent shark, 1 medium angel, 1 giant danio, and 1 little orange fish #not sure of the name#. Well, 4 of them have died, the giant danio is still healthy. One week later, I bought 1 pink kissing gourami and 1 spotted catfish. Another week went by and I bought a large plecostomus and a gold gourami. Finally, two days ago I bought a huge plecostomus, a blue gourami, and a Chinese algae eater. I decided to buy a test kit, a water conditioner, and a nitrate remover#removes nitrates, nitrites, ammonia, chloramines, and chlorine#. Yesterday, I tested the water with one of the strips and everything is normal except for the nitrites. They're atleast 50 ppm. I've used the nitrate remover and no results. I need help with removing the nitrite. I've heard that the fewer the chemicals the better you are, therefore I'm not using anymore nitrate remover. Please help. :

Answer
You put too many fish in your tank at once. Also you are never suppose to cycle a tank with angel fish or iridescent shark due to their sensitivity. If your tank was cycled they would go in your tank perfectly, but it is not quite yet. Do not do a full water change. Doing so will wipe out your beneficial bacteria you built up in your aquarium. Instead, do partial water changes to bring down the nitrite level. Unless you do water changes, it will continue to build up and that is not what you want at all. Nitrites can cause severe stress which can lead to diseases. Continue to test your water periodically. It is important to test your water for each substance individually as part of your routine aquarium maintenance to asure no slip ups. Any other questions feel free to ask and good luck. :)