I found this:
"With sensitive fish (such as Clown Loaches) it is imperative that you are careful with most ich treatments. Malachite Green is more dangerous to these fish, however if used in a buffered form such as ParaGuard or Medicated Wonder Shells it is less toxic. You may also use Triple Sulfa at the same time to further buffer the MG (I and many of my colleagues have used this method considerably for Clown Loaches, Elephant Nose, ect. with good results). Another VERY important aspect that is often forgotten is that Malachite Green is much more toxic at lower pH (especially on the acid side of the pH algorithm). Calcium is VERY important to buffer this as well (calcium also improves osmoregulation, see this article: http://www.americanaquariumproducts.com/... ) Malachite Green is generally safe (long as it is zinc free) for shrimp, crabs, & snails. Be careful with Copper though You should not have any problems with your bio filtration as it would take massive doses of MG to affect the primarily gram positive nitrifying bacteria. Methylene Blue, Tetracycline, Erythromycin and others that are primarily gram positive are more dangerous to your bio filter. "
https://answers.yahoo.com/question/index;_ylt=A0LEV7_psZZW7QgAXSonnIlQ;_ylu=X3oDMTByNXM5bzY5BGNvbG8DYmYxBHBvcwMzBHZ0aWQDBHNlYwNzcg--?qid=20071007101126AAMrReE&p=%22malachite%20green%22%20shrimp%20safe%3F
Unfortunately, my chemistry knowledge sucks, so someone else may have to help if you have questions regarding that.