In case nobody noticed, rscottbc lives in BRITISH COLUMBIA!
An Ace 150 0r 250 is NOT what to use in that area, there is way tooo much iron in that soil~!
I owned an Ace 250 and I too live in the heavy iron belt just like rs. He will be lucky if he gets 4 inches on a nickel. Additionally, there is a German site that has tested the 150 and the 250 side-by-side and found litttle if any difference in depth in mild soil, but that is MILD soil and BC has really B-A-D soil! I read and speak German, but people don't need to know it to read the number stats on the site.
rs, you need something that has a decent ground balance on it, otherwise you'll be just like me when I gave mine to my daughter because it performed so poorly in this area. It's one year later and she still hasn't used it. It would work ok in wood chips or sawdust but you will want something else within a day of doing just that.. Get a different detector. Try a low-priced Minelab or Whites, they will work MUCH better here.
Those Garrett aces work very well in the Eastern US, the deep south, Florida, and most of Europe, but as with most Garretts now, they really suck in this (our) soil from the Rocky Mountains westward. It's because there was an (iron) meteor shower some 10,000 years ago in the western N. America Continent. A good detectorist already knows this and someone should have told you already.. Garrett had to upgrade all their high-end detectors with new add-on chips because of the complaints here and other places that have such rotten soil.
If the German site can't easily be found I'll look for it again and post it here.
Good luck