Denise-
First of all, you shouldn't use salt because you have a frog and a pleco who will not handle salt well and most of the ich medications contain medications which are going to be hard on your tetras. There is a medication called Quick Cure that you can use that is Formalin and Malachite Green that you can use but will have to cut to half dosage for the tetras. If the outbreak is severe, then I would recommend a medication called Clout. Velvet also usually needs a dark aquarium as the parasite thrives on light. put a dark colored garbage bag loosely over the aquarium or towels or something that lights will not penetrate and feed and medicate and cover as quickly as possible.
If the Ich Guard that you have has the active ingredients of Formalin and Malachite Green then you can use it with no problem on the tank but use half the recommended dose for the tetras or you will have them stressed.
You will also have to raise the temperature and run the airstone at a high level and leave it there for 14 days for the ich. Also remember to remove the carbon from your filter.
Rose
