Yes, the parasitic ones would be more interesting since they need to hunt and get bigger.brook lamprey are not parasitic as adults. they only eat as larva, then as adult's they're only task is to spawn. the lampreys that are parasitic such as sea and the silvers i posted as adults would probably be more interesting especially considering they are behemoths compared to many brook lamprey species
You're correct about the brook lampreys not feeding when they reach adulthood and only spawning; they also develop eyes once they hit adulthood.