Quick Cure or Quick Kill?

Dear Blue Lobster:

I have a Blue Crayfish in my tank with several Cichlids and two Plecos. A recent fish purchase has put my tank in chaos and have already had 3 fish lost to a fungus, parasite, or disease. I purchased a product at my local fish store but it doesn't appear to be doing ANY good. After some research online I have decided to dose my 100 gallon tank with "Quick Cure" which contain malachite gree and formalin. From what I've seen online it may "harm invertebrates." 1) Will my Blue Crayfish be harmed? 2) If he will be harmed, what is the best course of action to take to save my fish and keep my handsome crayfish safe? A quarantine tank? I love your posts. Thank you for your help

Crayfish mom

Dear Gentle Sir:

Quick Cure works by poisoning the less complex organisms in your tank. Plants survive only because of their cell wall, which other organisms lack, and vertebrates have complex enough metabolism to detoxify the active ingredients in Quick Cure. Any invertebrate or fungus will be wiped out.

A quarantine tank will work for to keep your cray out of the toxic soup, but knowing when it's safe to return it to the tank is another matter entirely. The composition of your tank is important to consider.

Do you have a clay substrate? Are the rocks in your tank hard or soft? If you have aquarium plants, do they fix compounds from the water? All of the above may absorb and then slowly leach the Quick Cure back into your water, slowly poisoning your crayfish.

Another alternative would be to remove all the fish from your tank, leaving your crayfish the sole tenant of those premises. You could then add some ghost shrimp and have a crustacean-only tank. An aquarium without fish is an aquarium without problems, and all the better for your cray.