25% of how many gallons? You should always at least use Reverse Osmosis water. I do a 30% water change every two weeks. We need more info. Sizes, what's in the tank, do you do weekly tests, what are the levels?
it's a 48 gallon reef aquarium that i aquired from a friend. the ammonium level is a bit high as is the nitrate/nitirite. Also, the ph level is a bit low.
