Just wondering what the nitrate levels of your goldfish tanks are right before you do a water change? Asking this for those with fully cycled tanks only that have zero ammonia and nitrite levels. I haven't done a water change for about 8 days and it is somewhere between 5-10 ppm. I am just wondering if this is alright for fancy goldfish. What is the most you'd let it get up to before you do a 50% change?