Lead

Lead (Pb) is a soft, heavy, toxic and malleable metal, which is bluish white when freshly cut but tarnishes to dull gray when exposed to air. Lead is a potent neurotoxin which accumulates in soft tissues and bone of living creatures over time.

Lead is often used in aquarium tanks as small strips of metal used to weigh down items like plants and air tubes.

Note
Lead is a poisonous metal that can damage nerve connections (especially in young children) and cause blood and brain disorders. So these objects should be kept safely out of the way of the young.

Lead is a banned metal in most countries and is becoming more so. It is reasonably expected that 'lead weights' in the near future will be replaced by some safe material.


 * Many so called 'lead weights' are in fact made out of Magnesium or zinc. You can test this, by holding a suspect lead weight over a flame. It will burn bright green if it is zinc, lead burns with a blue flame. Note if it is lead then the flumes are toxic! So make sure the room is very well ventilated.

Zinc will slowly react with water with a pH of less than 7 but it simply releases low quantities of hydrogen into the water which quickly floats out of the water.

Is it safe to use in an aquarium?
Lead naturally builds a protective layer of lead oxide (a dull grey colour) and this layer stops the lead from leaking into the water. However if your tank pH is less than 7 then the slightly acidic water will slow corrode away this protective layer and will leach lead into the water. But at a pH of around 6-7 this will happen so slowly over several months that you will probably have done several 25% water changes over that time thereby removing any small levels of lead there may have been in the water.


 * Invertebrates like shrimp, triops, snails, crabs, etc. are very sensitive to levels of any heavy metals and the presence of dissolved lead in the water will kill them.


 * Some commercial water conditioners have the ability to de-toxify heavy metals dissolved in the water.

Links

 * Wikipedia
 * APD - Caution with lead weights