Okay I just tested my water and the tap runs at 7.0 or 7.2 I can't exactly remember (I'll check) and the water that is in the fish tank is higher than 7.6. I don't know how much higher because my scale ended at 7.6. The water's only been in the tank a week and all that's added is Aquarium salt. I put the aquarium salt in there when I noticed that I had some nitrites. What should I do to make my water suitable again and keep it from being unstable and harming my fish?

Hi again,

Firstly, you need to find our exactly how high the pH in your tank is. Get a high range pH test kit (these usually go up to 9.5) and check it. If the pH level is 8.2 or less than that's fine, if it is more then it is extremely dangerous.

What you need to do is buffer the water to stop the pH swinging like this, which is easily achieved by adding baking soda to the tank when you do water changes.

However, what I'm NOT sure about in the case of your water - and I am hoping that someone else here will be able to tell you! - is whether adding soda to the water will keep the tank at the tap level pH of 7-7.2, or whether it will send the pH level up to whatever it is in the tank (i.e. somewhere higher than 7.6) and hold it there.

Hopefully, someone can shed a bit more light on this - sorry I haven't been much use!