Formalin in Koi Ponds, Fish Tanks How to use Formalin:

Try not to leave Formalin in a system unless you have to. Don’t use formalin in very warm, or very cold water. Don’t use formalin unless you accept the consequences, or unless you have expert assistance on hand. How to use Formalin: Formalin 37% should be used as a long term treatment for ornamental fish … Read more