First, nitrates are not toxic. They are an overall measure of the balance of the tank. If they were high, the tank was very unbalanced, and most likely had a lot of organic matter. This drives pH and alkalinity down, as well as oxygen levels. In any case, yes, this medication will harm shrimp (crustaceans), invertebrates and mollusks. Treating fish as a preventative rarely is beneficial. It is recommended with marine fish because most are wild caught. In regards to freshwater fish which comes from farms, typically there is no benefit, but if you really want to treat them, it is best to do so in a quarantine tank, and for three weeks. Parasites have a life cycle of 7-21 days.
Date published: 2018-05-30