First, I've no experience with the test strips.... get that out in the open first.
Second, they are apparently notorious for being incorrect BUT I expect that they are just off in accuracy as opposed to being totally wrong due to humidity in the air affecting the chemicals on the paper. By how much and in which direction, I don't know.
If your nitrates are actually 100 ppm then you need a substantial water change, 50%, which will still only bring them down to 50ppm. Test again tomorrow and change again if it still reads high. 10 - 20 is better but in your case, anything lower is a start.
If you've never tested before, then the strips are a step in the right direction. It would be best to use a liquid test kit (API Master test does ammonia, nitrite, nitrate and pH and there is a separate kit for hardness) but not critical.
Ich, from what I've read about it, usually comes about due to stress in the fish. The high nitrates may be involved and will need to be lowered in order to help the problem. Others may have better advice than this.
Oh, you should post this in the aquarium section as there is more traffic over there and you will get a better response.
Last edited by JDM; 01-24-2013 at 09:07 AM..