Chelation is the pharmaceutical process of bonding a mineral to an amino acid to make it easier for the body to digest, assimilate and utilize it.

Chelated minerals, or chelates for short, are designed to mimic the way minerals occur naturally in the diet as well.

Chelated iron, while not as widely known as iron sulfate, is ten to fifteen times more bioavailable per mg than other types of dietary iron supplements.

I don't know how this relates to aquarium's but hope it helps.
Interesting concept.

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