Don't change all the water at the same time. Turn off the filter and change the filter cartridge. Put in the fresh, treated water and turn the filter back on. Replacing all the water in the tank is not healthy for your fish unless it's absolutely necessary. You can change anywhere from 1/4 to 2/3's of the water, depending on how often you perform water changes, but I wouldn't change it all.How can change the water for my fish without poisoning the water that was in the filter?i dont understand, you change the water, by taking the fish out and put them in a separate bowl, clean the tank and put them back in. i have had fish all my life, how on earth do you poison the water?How can change the water for my fish without poisoning the water that was in the filter?Just make sure the water isnt pure tap. Let it sit out for a day or 2 because a drastic change in the pH of the water can harm your fish. When you let it sit the chlorine and other chemicals evaporate.How can change the water for my fish without poisoning the water that was in the filter?Don't worry about %26quot;poisoning%26quot; - just change water in small batches and if you use tap water, let it sit for 24-48 hours for the chlorine to dissipate before adding to the tank.
Even more important than ph is temperature. Quick changes in temperature can shock fish and make them sick. When you see things like spots on the fish (called Ich) that's a sign of temperature or other issues that stress the fish and make them vulnerable.
