Originally Posted by meggyb27
i did a ph test to the tap water before filling the tank (let it set for awile) and it was 7.0 then did it 2 days ago to the tank water and it was 7.8, then did it just a coupe of minutes ago and it was 7.6
That is probably OK. First, when you test the tap water, let it stand overnight in a glass or jar, then test; you may get a different (higher) number. I still suggest doing this, because I am assuming the tap is a bit higher, closer to the 7.6 of the tank, and this will confirm that. In which case you are certainly OK, as goldfish do best around these numbers (mid-7's).
If the overnight test is still lower, say 7, I would then monitor the tank over several days/week, testing maybe alternate days. This will tell if the pH is moving at all, and how much and in what direction.
Always test tank water pH the same time each day. Such as early morning, or around noon, or evening. Try to use daylight to read the colour, as artificial light will distort the colours various ways. The reason for doing the pH test at the same time each day is because pH naturally fluctuates diurnally; it will be lower at dawn after the darkness of night, and highest at the end of the day. This occurs in nature as well as the aquarium, and is minimal; but you still will likely get a different reading between early morning and early evening, so testing the same time each day will let you see just how much it is changing from the aspect of stability. This is likely the reason you have 7.8 and 7.6 for instance. Some relatively minor fluctuation is to be expected.