EDTA
Ethylenediaminetacetic acid ["acetic acid"], Titriplex II, complexing agent (chelator)
Even the free acid has only a low acute toxicity. The LC50 of Lepomis macrochirus (bluegill sunfish) is 159 mg/l, that of the alga Sc. quadricauda is 11 mg/l.
For the iron complex, these values are generally beyond aquaristically relevant concentrations.
The EC50 for water fleas and bacteria, for example, is in the order of g/l.