Howdy Larry! Well, for a more authentic look you might try and get hold of
an aluminium XXXX can - most folks I know here in Oz only drink Fosters
when desperate. Fosters is the crap we export because it isn't good enough
for local consumption. :)
That applies to Rainbow habitat - in the cooler southern climes I inhabit
it would have to be Victoria Bitter (an attractive green can, pity the beer
didn't taste better but at least it isn't Fosters).
I think that the aluminium can is your best bet - the paper lables on the
375ml stubbies are going to get messy when they start to disintegrate -
unless you have some clear fish-safe epoxy to seal the lables with.
Upmarket tanks may wish to go to Crown Lager bottles, (and although
geographically incorrect may serve nicely to breed Desert Gobies in), which
is chemically indistinguishable from Fosters, but does taste a bit better
owing to a different finishing process.