I spent a lot of time experimenting with the different kits, and lost some fish that didn't need to die by using the wrong test kits. . You can not use a Red Sea test kit with Cupramine and get accurate readings. Plaz, you are correct that the red sea kit will show a level of .5 when the Seachem kit shows less. I believe this why some people do not succeed using Cupramine. They use the wrong test kit. I did so many tests with various kits that I am confident in making this statement. I used Seachem, Red Sea and Aquarium Pharmaceuticals test kits daily in two different batches of fish. Invariably the kits by other manufacturers show that I was at .5 ppm, when the Seachem kit showed that I was too low. I was afraid to trust the Seachem kit, so I used the Red Sea kit. Consequently, the Ich continued and I lost several fish. I lost 9 fish before I decided to totally rely on the Seachem kit. In no time at all, the Ich died, and the remaining fish are still in my tank, 1 1/2 years later. Aquarium Pharmaceuticals was the worst for Cupramine, yet I like their kits for other types of tests. You will waste valuable time and cause your treatment of Ich to take longer than it needs to, and you will probably kill some fish (like I did) that didn't need to die in the process. You should only use a Seachem kit when using Cupramine, no exceptions. Use the sample water that comes with every kit if you don't trust the kit. If your out of sample water, go buy a new kit. If you have an old kit, go buy a new one. This is CHEAP compared to all the wasted work and time and loss of fish.
Plaz, with only knowing the little you posted here, I would still suggest that you were under the level you should have been with the Cupramine. I worked very hard with all these kits, and had many conversations with the chemists at Seachem. They were interested in the tests I was doing between the different kits also. Their product has other ingredients that will throw off a Red Sea kit. I feel it's wrong to recommend using a different manufacturers test kit to test their product, and will very possibly stretch out what should be an easy process, along with the deaths that occur as the time line increases. I hope I am not coming across negatively, or narrow minded. I just spent a lot of time on this topic and feel I am very qualified to give solid advice on it. I am very passionate and convinced on what I learned about this.
Pecan, you will have to keep adding Cupramine until you hit the .5 level. Don't be afraid to go over. I went over once, up to .8, which is the highest they recommend. The color on the chart is very obvious when you get that high. To remedy it, I just did a partial water change. I brought it down to about .6, and in two days it lowered to .5 by absorbing into the rock and sand. The dosage Seachem gives is VERY conservative. I have had to use twice the amount recommended to reach therapeutic levels, and once 4 times as much (this was in a 120 gallon tank with substrate and old rock) to get the levels set. Just test after every additional dose. I follow the stated procedure for the first two days, then dose daily, and towards the end, when I'm narrowing it down, say from .3 to .5, I will do two doses or more in a day. Then, you'll still may have to do a dose or two once you get it to .5, as some of it will be absorbed into substrate or dead rock.