Not quite sure how things work in the US, but here in SA military stuff that's shipped cross border does not have to go through the same customs and port health shit that normal freight has to...
Where are you being deployed to boet? Or is that still an uncertainty?
Most military units deployed to 3rd world countries ship their own rations as well, seeing as the soldiers quite literally cant "stomach" the water and so called fresh produce of said countries. My point is...water does get shipped...and i doubt seriously whether tropical water constitutes as a bio-hazard (then again, some people's tanks are a bio-hazard on their own

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I work for a courier company...and anything...i mean anything can get shipped (some more legal than others it might be said), so if you want to ship your fish...do it! Get a military vet (you must have some contacts) to quarantine and release a clean bill certificate before you leave...get hold of the officer in charge of freight forwarding seeing as you say they ship personal effects up to a certain weight for free, and advise him/her of the fish you wanna ship (which i doubt would be a problem). Crate your tank...if you just wrap it in bubble wrap or whatever it IS gonna brake...so crate it and you're good to go.
Like i said, i'm not sure on US military protocol...but here in SA its not that big an issue