I purchased this product to treat ich (ichthyophthirius) outbreak in my outdoor goldfish/koi pond. After using and reading more about how copper ion works and about ichthyophthirius, I am confident that this product will not cure your fish once they are already infected by ichthyophthirius. Ichthyophtirius burrow under the fish epithelial cells, and the active Cu2+ ions cannot penetrate the cell membrane. What this product does is to kill the free swiming theronts, after they burst out from the infected fish. Whether the fish can survive totally depends on its own. That's why this product asks for a 14day treatment. Ichthyophthirius is so contagious and deadly to goldfish and koi, once you see the fish flashing, hiding, especially showing white spots, it is on its way to death if you use this product: my goldfish and koi that showed symptoms were all dead (12 out of 12)! The remaining ones seem to be immune to ich from the beginning. The Cu2+ ion concentration is also very sensitive to pH and to other reducing agents in water. The 0.25mg/L concentration is too low to measure accurately using test kits that use color comparison by eye. If your tank water has some light brown or green color it will confuse you more. Basically, it is hard to know the concentration of the Cu2+ ion in water after applying it, let alone make sure the Cu2+ stays for 14 days. I ended up changing the water every 3days with fresh treatment. If you have goldfish or koi starting to show ich symptoms, use products having malachite green in a hospital tank, you may be able to save them but not guaranteed.I wish the instructions were a little bit more self explanatory but other than that it's ok. Testing levels of it concentration could be a little hard unless you go with a fancy tester. Also feel that for the price it should come at least with a tester for the first a few Test.Fish came down with a bad case of ich in my planted rainbowfish tank. The ich made it past the quarantine process and ended up in the DT. I treated two tanks simultaneously, one with Hikari Ich-X (malachite green and formalin) and the other tank only with Cupramine. The tank with Ich-X eventually cleared after approximately 6 days and daily treatments, two lost fish and tank stained blue green. The other tank that was treated with Cupramine had no losses (and there are Amano shrimp, Otos and Corys int hat tank). Started with the recommended dose of 0.25 mg/L for freshwater dosed over 48 hours. Since the fish showed negative signs or stress, I upped the dose to 0.5ppm over the next couple of days. I used a Seachem copper test kit and measured CAREFULLY as I have read reports of overdosing nuking fish. After 10 days there are no fish or invert losses, fish have no evidence of ich both on the skin or in the gills (no labored breathing). I will complete the recommended dosage time of 14 days and add Matrix carbon to the filters to clear out the Cupramine.The Pros of using this medication are:- It does not stain like Formalin.Malachite Green treatments- Only one treatment needed (dosed over a few days) as the medication remains in the tank and sits there in the waiter waiting for the disgusting ich swarmers to hatch so they can be annihilated!- Cost effective as I only needed about 24ml in a 125 gallon tank (plus 5 gallons of filtration volume) to achieve a treatment dose fo 0.5ppm. I would have had to dose 65ml PER DOSE of Paraguard , DAILY for 28 days! Thats 1,820ml of Paraguard!!!Cons:- DO NOT use if you are lazy, this requires measurement of copper to confirm dosage.- Can't think of any other cons to using this product. I will switch to using this instead of Formalin/Malachite in my quarantine tank from now on.I liked how easy to use this was. I had a planted aquarium with only plants and I had a snail issue. They were reproducing really fast in comparison to my water change schedule. Treated the water with this, and the issue has been resolved.Cupramine is a highly effective copper based treatment for Ich -- a truly aweful disease that was about to wipe out all the goldfish and Koi in my tank. It's a large tank and I appreciated that it takes so little of this treatment. It's very economical which is important because with Ich the whole tank must be treated, not just the fish so you cannot use a small hospital tank unless you are willing to keep the fish in the hospital for many weeks (the parasites will eventually die in the display tank without treatment if there are no fish for them to infect but it takes a while to be sure). You can see the fish do not like the medicine. After the first half dose two smaller Koi died from the treatment (ironically they had been doing best against the Ich before that). I was quite worried about what would happen after the second dose was added, but there were no further fatalities even after the second dose though the fish were lethartic and stopped or slowed eating. Obviously they felt sick. But once the Ich was gone (it takes a few weeks for all parasites to enter their vulnerable life phase), I started the water changes and all the fish bounced back. Cupramine is strong medicine for a bad disease. It's not to be used lightly but effective if you need it and very reasonable in cost even for large tanks. A side benefit is it's tough on algae.El producto es de los mejores, de una marca reconocida y con unos resultados excelentes, ya había probado en otras ocasiones este producto. El problema en esta ocasión es que venía abierto y con derrames (conocidos desde el centro de distribución). Siendo una medicación para animales, debería siempre estar con el precinto intacto. Hable con Amazon explicando el problema y me lo cambiaron. Bajo mi punto de vista, el control de calidad no debió permitir que saliera ese producto del almacén. La calidad del producto que me llegó no era digna de la marca que representa.Tres bon produit je m’en sert souvent