I believe 90% of us here use fishfinders, if not approaching 95%. We have people using Garmin units, Humminbird (I'm using the 718), Fish Buddy (Hummingbird), Lowrance, etc..
It's all about what frame you're planning to create for you tube, what gear you're planning to haul, how much weight capacity you have left, and what's your budget for sonar needs. It appears you've chosen the Garmin 150, which is a great entry level float tube sonar for search and haul excursions.
Let us know what's your budget, and where you want to mount your sonar (front, or side). We all have different mounting approaches.