Help - Fish are dying

[plankton]

No, malachite green is not a 'form of copper', but a dye. Said dye is toxic to some fish (fresh water tetras, catfish) and a carcinogen to humans.

Here is a very good summary of Malachite Green on WetWebMedia:

Malachine Green on WWM

 

[philter4]

Malachite in the malachite green comes from the copper mineral and it is very toxic to all animals overdosing a stressed fish will kill them quickly

 

[D&KSac]

Just so you guys know i was in exotic this weekend and they are fighting some parasite that is killing there middle section of fish only tanks. I don't want to pretent or imply that is whats happenning here just FYI.

 

[plankton]

philter4 - yes toxic, but the 'malachite' in malachite green does _not_ come from the mineral.

"Malachite green is used to dye materials like silk, leather, and paper. The chemical known as malachite green does not actually contain the mineral malachite â€" the name comes from the similarity of color."