When copper sulfate is used in aquatic products, ferrous sulfate is often added. Half a catty of copper sulfate combined with ferrous sulfate is usually sprinkled at the dosage of 0.7ppm. Due to its wide use, many farmers mistakenly think that ferrous sulfate can kill insects. In fact, ferrous sulfate does not kill insects at all. On the contrary, excessive use will also affect the phosphorus content in water.

There are two kinds of ferrous sulfate: one is white powder, which has no taste and will be weathered in dry air, so it is called anhydrous ferrous sulfate; the other is our commonly used light green crystal ferrous sulfate, which contains crystal water, commonly known as "green alum", which has a pungent taste. The water solution is light green, which is a bit like the blue black ink we use to write with pen.

The wastewater treatment plant will use ferrous sulfate to remove the phosphate in the water and purify the water to prevent eutrophication. In aquatic products, it is more used to eliminate the fixatives on the skin surface of fish, make the mucosal cells fall off, increase the contact between drugs and lesions and parasites, and increase the permeability of drugs. For example, the rotten gills and gill filaments caused by some parasites are inflamed and swollen, and a lot of mucus is attached. If these mucus are not removed, when topical insecticides are used, these mucus will become the natural protective agent of parasites, hindering the contact between drugs and insects. For example, the ciliate parasites such as cryptotrichimna branchialis, filariasis, Trichuris, pityriasis, Trichuris and gobiella lingualis are easy to affect the efficacy due to mucus. Now many companies are studying how to improve the solubilization and permeability.

Attention should be paid to the use of ferrous sulfate in aquatic products: snakehead is very sensitive to this drug, but it can be used at the dose of 0.2ppm in other fish. In addition, when ferrous sulfate is used in water and quinolones are mixed in feed, the absorption of drug concentration will be affected.