It depends on what is the cause. Bacteria colonies are kept in check by a controlling factor: space, food, temperature, predation and oxygen are the big ones. Food is a common one, but predation is important as well. If you increase the food source, or remove the predators, the bacteria colonies will expand until either the food source drops (ie the bacteria consume it all or it's manually removed from the tank), or the predator population is re-established. Without knowing what is the factor, it can be tough to determine the solution. Most often in my experience, blooms are precipitated by a sudden change in the system--but that change may be something like a new water source, a different food, a dead animal/plant in the system, or even OTS, where the pH suddenly drops enough to impact micro life.
