What do you do with spare tanks?
Tanks have never been the problem.
Well, theft of Tanks, at least. There is no market on the island to sell them.
Gathering enough Tanks for a bunch of divers to do, say 3 dives, THAT can be an issue at some of the resorts.
On a busy week there are often not enough tanks topped off for that.
Gathering a couple Extra Tanks, just in case one of those tanks has a bad valve, that too may raise some eyebrows.
Tank valves that are not exactly perfect (O rings, neck leaks, etc), THAT too can be and issue on Bonaire. Look closely.
We divers are not always as careful with rental gear, as when we use our own gear, and Bonaire shore diving means that rental tanks can get a LOT of both use and ab-use, in a very short time! Always grab an extra tank or 2 ( be sneaky, as this is discouraged by all ops), and grabbing them the night before may bite you in the butt the next morning, when you arrive at that choice dive site, only to discover that one of those nice "overfills" you found the afternoon before, now only show @2300#, or less.