Ick is nasty. It can block the gills from getting oxygen, and it irritates the fish's skin, so they will bounch off rocks, ornaments, etc. This is known as flashing. Sometimes the fish will stay at the surface where the filter runoff is, or to gasp for some air as they are suffocating.
Fish can live with ick in their tanks, but as soon as their immune gets weak enough, the disease will strike. The best way I have found to deal with ick is to prevent the fish from being stressed out any way you can. For instance, I found that when I was doing water changes, I was using straight cold water. The sudden temperature change stressed the fish out, and when they get stressed their immune gets weak. So I use luke warm water instead. I don't know if your case is the water changes in particular, but something you might be doing could be stressing your fish out. It could be the fact that they are new in their home as well.
You could try some medication like Ick Gaurd (or whatever ick controle you can get) to help keep the ick at bay until the fish get used to their surroundings.
You could also try the salt and high temperature treatment, but it's not recommended with yout Tetras. Tetras do not like both salt and high temperature.