Preservation
use 70% alcohol for preservation (or at least maintenance of perservation) of our specimens...this is diluted from the 95% stuff we keep on hand in the lab. the actual preservation/fixation, however, is done with formaldehyde. if the fish is larger than just a few inches then i cut the belly so the chemical can enter into the insides of the fish and preserve everything. the fish stays in the form. solution for a couple days. if its a gar or bichir, a fish that has rigid bony scales, then i take the fish out after 2-3 days and just let it air dry. the fish is now dry preserved.
if doing a standard preservation i take the fish out after 2-3 days and let it sit in a container of water to soak out the formalin. after a day in the water the fish is removed and placed into a container of 70% alcohol for long-term preservation.
as far as using other alcohol, i think as long as its relatively pure and the proof is about 140 you should be ok...in theory --