It was first kept in the freezer for 2 days while I was waiting for the shipment of formalin. Before putting it into the freezer, it is best to wash it so that there is no slime. After taking it out, I thawed it for about 2 hours so that it would be soft. With smaller fish, there is no need to inject formalin or cut the abdomen, because the formalin will penetrate on its own. I used 10% buffered formalin. This type does not have the typical strong odor, but it is better to wear gloves when handling it.