In natural fresh waters silica (mostly as otho-silicates) are next to carbonates in abundance. Possibly silica is also formed in a small quantity as complex alumino-silicate ions. The major source of silica is through dissolution of rocks in drainage basins. Silica is most important in fish ponds because of its influence on diatom growth. Silica is removed by plankton blooms and it gets back into water when diatoms die possibly by simple decomposition.