Will adding aquarium salt lower the ph level from 8.5 the tank is a tropical 35 liter?
What is your pH out of the tap? If it’s lower then it something in your tank buffering the pH to a higher level. Avoid decor from the beach – this is likely to buffer your pH even higher. Seawater has a naturally high pH and things like seashells leach calcium into the water thus raising the pH (some types of rock also have the same action). Check all your decor is not buffering your pH higher. If you have unidentified rocks or shells, remove them and see what happens. Do not rush to change the pH however, fish can die from pH shock.