From reading your original post it sounds like you haven't cycled the tank. If you filled it with water, added cycle and fish then your tank isn't cycled and you're going to run into alot of problems. Having compatible fish is important but the ones you have will either die or get very weak if you don't cycle your tank. If you want to cycle your tank with fish get only one and a liquid test kit. Ammonia will spike first, then nitrite and finally your readings will be 0 for each. A & N are highly toxic to the fish. Take all of the fish back and get a test kit and read up on cycling the tank. The cycle you added doesn't work and I guess it was more bad advice from the store you went to. Bacteria needs to be refrigerated to be kept alive and isn't cycle right off the shelf? If you're going to do this with a fish add lots of live plants. Just float them, they'll help to take up the ammonia, nitrites and nitrate. You can remove them later if you choose to not have plants but it will make it easier on the fish.