In the closed environments that we call aquariums, it’s not uncommon that we experience blooms of cyanobacteria, diatoms, or some other maligned organism, despite not introducing anything for months. The reality is that these organisms are almost always present, though their numbers are so low that we just don’t notice. Then when the first nitrate or phosphate spike occurs, their population explodes and then it becomes really noticeable. As with any nutrient driven growth, the cyano or whatever it is that’s growing doesn’t immediately go away with water changes. Instead, it takes a more methodical approach of nutrient reduction to get your aquarium back to its pristing condition.