I have a 10g QT tank with a aqueon HOB filter, canopy light, heater, power head and couple of hiding places for the fish. Have two clown fish and a purple dotiback waiting to be placed in my display tank. I've had them in observations for two weeks. I check the parameters in it at least every other day and when necessary do a water wchange. Thing is today when I check the numbers they are off the chart. Amonia = .50, nitrite = well over 5.0, nitrate = 20 and this is after a 25% water change. My question is how often can I do water changes and how much can I change without putting the fish in danger of shock. Thanks for your response.