Will Formalin Kill Beneficial Bacteria?

Formaldehyde acts as disinfectant as well as biocide. An aqueous solution of formaldehyde can be useful to kill most bacteria and fungi.

What kills beneficial bacteria in aquarium?

Unfortunately, chlorine and chloramine will not only harm aquarium fish but can affect the entire aquarium system. These chemicals also kill beneficial bacteria and impair biological filtration.

Can formalin kill bacteria?

Formalin is a 37% solution of formaldehyde gas in water. Diluted to 5% formaldehyde it is an effective disinfectant; at 0.2% - 0.4% it can inactivate bacteria and viruses. Unlike chlorine, formalin does not corrode stainless steel.