There are not many metals that may be utilized unreservedly in water. Lead is the very best, and it could be utilized extensively, but regrettably it is not rigid sufficient for some of the uses to which we would like to put it. Steer clear of brass, galvanized iron, and zinc, as they corrode and poison the water.
If your aquarium has a brass frame, the only component that may trigger trouble is the top inside edge, the remainder of the frame is insulated by cement and glass. Cover this edge with cement or paint.
Iron will rust and, even though it is not poisonous, drops of rusty water falling into the tank aren’t very desirable, so you should treat iron frames with cement or paint.
Nickel plating corrodes after a spell in water; so it should not be relied upon as a permanent protection.