High pH level

Question
pH level showing 8.4 .  Have been using pH down but this does not seem to be helping the problem.  Tank (25 gal) was filled with tap water and has been cycling for approx 2 weeks with no fish.  Any suggestions?

Answer
For one, you cannot cycle a tank without fish or an ammonia source like fish food and/or ammonium.

Here is an article on cycling:
http://www.aquaticcommunity.com/aquarium/cycling.php

Why would you want to lower the pH? Changing the pH with chemicals is not required and is REALLY dangerous. All freshwater fish can stand most pH levels (with the exception of some angelfish and discus) and messing with the levels will cause problems and can crash your tank.

The reason that it is not causing any change is because you have a high carbonate hardness (kH) level. High kH levels mean that the water is very hard and resistant to pH changes.

John Kliewer