metal in an aquarium

Roger Sleet wrote:

Silver is fine in both salt and fresh.

If you're going to spend the buck for silver, I think you should go with
titanium. It's ion is non toxic and it's much more inert.

In fresh you can also use iron,
steel, (preferably stainless) and aluminium. Avoid copper, lead, brass,
bronze etc. as they can dissolve and are toxic.

When we're talking about car cooling system, aluminum engine block needs
extra attention to prevent corrosion since they're more vulnerable to
corrosion than iron engine blocks.

Doesn't that mean aluminum objects are vulnerable to corrosion in aquarium
too?

Well in the car engines, the burning gasses create acidic conditions which
can cause the aluminum to corrode. Don't think we need worry about that.
Still aluminum is soft and will corrode in water from pure oxidation, so
stay with the silver. Even if some dissolves, it is a natural antibiotic
and may help your fish