Most of all lamprey species are freshwater and most of them are actually non-parasitic. To my knowledge when I studied them in college there were 46 total worldwide of which only 5 are saltwater, and all of them are parasitic. The remaining 41 are freshwater and of those only 13 are parasitic, which means 28 are non parasitic, also called Brook Lampreys. They are the ones he is referring too the juveniles are referred to as ammocoetes. They live in the sediment in backwaters and filter feed for several years without a buccal disk/sucker mouth. Then they metamorphose during the winter to adults and look like your typical lamprey sucker mouth but they are semelparous so they breed and then consequently die without eating as adults.
Also for keeping the trout in an aquarium is pretty rough as the warmer temps usually lead to disease. If you would like to know more check out some of the local fish hatcheries in PA. They stock millions of trout and while they have lots of neat ways to raise them they typically use springs to keep them cooler and avoid disease. If your going to try it then def do the rainbows as the can take temp to low 60's as long as the O2 is high enough.