Phosphate, the ultimate culprit, or low-phosphate food for clear water?
As phosphates are crucial to algae growth, phosphates are perceived as an enemy. This, though, is not the case, as phosphorus in the form of phosphates is important for all organisms, because phosphates play key roles in the entire energy metabolism. Specifically: Without phosphates, there would be no life on Earth.
Therefore, do not be misled by advertising slogans like “low-phosphate food for clear water”. What, precisely, does this mean?
Either a fish needs to eat more to meet its phosphate needs, in which case there will be an increase in other excretory products which the fish cannot utilise. Therefore, the pond keeper must feed more. Or the fish will starve, until it finally starves to death. In that case, you might as well quit feeding the fish altogether!