Tricaine (3-amino benzoic acidethylester) comes in a powdered form from Sigma (Cat.# A-5040). Make tricaine solution for anesthetizing fish by combining the following in a glass bottle with a screw cap:

400 mg tricaine powder
97.9 ml DD water
~2.1 ml 1 M Tris (pH 9). Adjust pH to ~7.

Store this solution in the freezer. (Buy the smallest amount possible because tricaine gets old.) To use tricaine as an anesthetic combine the following in a 250 ml beaker:

4.2 ml tricaine solution
~100 ml clean tank water