[art_b]

Hi,

The gypsum (CaSO4 - 2H2O) on this website http://www.gypsum.co.nz/pages/product/ has a breakdown of major and minor components. Is this gypsum safe for aquarium use ?

Regards,

art_b

 

[Zapins]

CaSO4-2H2O dissociates in water to make Ca (+2) and SO4 (-2) - both necessary nutrients for plants. The chemical will work well in a fishtank.

However, the link you gave says the following:

"This product is of very high purity (93 to 98% calcium sulphate)."

93% is not very high quality and over a long period of time the byproducts might build up and cause harm.

Try look for lab grade CaSO4 (also known as calcium sulfate). Lab grade will be much higher purity, probably around 99%. Have a look on ebay or one of the sponsor links.