I have the same unit and have never got it to show any archs. Not trying to bash the unit because it is well worth the money for a starter unit. I have used the unit for over a year and it is great to find channels, flats, surface temp. and water depths. The best setting that I have found is the default setting. You will get a lot of replys that suggest turning off the fish i.d. and look for arches, slanted lines, vertical lines and horizontal lines. I use the round orange marker bouyies and noticed the angled line coming up from the bottom of the lake was showing fish on the line. The fish that the finder was showing was the large lead weight coming to the boat as I was winding it up. After that happened, I noticed that every time I trolled over a log. stump or limb under the water, the locator always showed it as fish on the screen. I have not read anywhere in the instructions that the fish will show up as arches. I have received several replies on another site that recommend all types of settings and determined that for this particular unit for my use is just use default and forget all the other settings. Just my opinion and I will but a nicer hb color unit in the future.