This is what we use here at the store and at Cory's fish room to treat every fish we come into contact with. For us we've never had problems using it with inverts, scaleless fish, and plants.
Commonly used to treat:
- Ich (Ichthyophthirius multifiliis)
- Velvet (Gold Dust Disease)
- Saproleniasis (Cotton Wool Disease)
- Fungal Issues
- Protozoan Caused Diseases
Contains: water, formaldehyde (>22%), methanol (>7.5), malachite green chloride (>0.2%). Dosage produces concentration of 0.5mg/L of malachite green and 15mg/L of formalin ~5.55mg/L of formaldehyde.
Either I wasn't dealing with Ich (although I've been an aquarist a looong time, and I believe I was) or this product just didn't make one damned bit of difference. Hiked the temp over 86 degrees and used as directed for TWO WEEKS to no effect on the one German Blue ram that seemed infected. Not one trophont dropped off. The appearance of the white spots never changed one bit. Finally treated the affected fish with a Formalin bath - old school. I'm a physician so I have easy access to medical grade Formalin. In the end, no other fish in the tank got a single spot (been 4 days since treatment halted) so I can't say anything definitive about the product except the treatment greatly exceeded the value of the one fish.
I have had great success using Ich-x to treat my fish for active ich outbreaks. It has even worked great for my puffers and fry tank. I highly recommend having this on hand, especially if you plan to get new fish.