metal mesh + saltwater = not a good idea

Should I assume you meant the nylon mesh? :wink:

You could use aluminum mesh, the nylon stuff isn't ideal as it stretches easily and can deform and break from the heat from the lights. If you got time you could also string your own net with a custom frame and fishing line.

I meant the aluminium mesh, but I am looking for something that has been coated with rust protection. Not sure if that exist or not though.

With full time job, couple fish tanks, a dog and a cat, I don't think I have the time and patience to string my own net :mrgreen:

My concern with the nylon mesh is also the heat from the light, plus if I want to frame it, won't be as easy as using the aluminium. (I know, I am a lazy person :redface:)

Aluminum will not rust or corrode so you don't need anything with a coating, it may be better to avoid a coating as it could come off and fall into the tank. Plain old aluminum would be best, when exposed to air a layer of aluminum oxide will form and protect the metal from corrosion, just keep it out of the water and you'll be fine.

All aluminum fish boats and aluminum lower legs have a piece of zinc attached to them.
This zinc becomes the sacrifical anode and corrodes before the aluminum. If you did not have this sacrifical anode, then the aluminum would oxidize and eventually the high priced boat would sink.
I would not use any aluminum anywhere near my aquarium. Splashes always occur.