25% a week is for regular maintenance, for a bacteria bloom, algae bloom, Nitrite or ammonia spike, you can increase your water changes with no problems, with nitrite and ammonia you SHOULD increase your water changes. You will here some say that you will loose any benificail bacterie from the water changes, BAH!, Most of your benificial bacteria is living in your gravel/sand bed, or in your filter on your pads, the amount of bacteria free floating in the water is very very miniscule and you should not worry about it.
White clouds - bacteria blooms - usually occur when a tank isnt fully cycled and you have introduced new fish
Green clouds - algae bloom - usually occur from too much light
Partial water changes will clear up both
I don't recommend chemical treatments for these two types of problems, they are not that hazardous to your fish.
Ammonia/nitrites require even more water changes and repeatd testing, high ammonia and nitrites will do more harm to your fish than any water change will ever do
Remember never do a full blown tank clean up. you will clean out all of your benifical bacteria, and basically set the cycle back to day 1
