will a magnet stick to cast iron tub

Yes, LED tubes are compatible with magnetic ballasts. In fact, many LED tube manufacturers design their products with the ability to work with both magnetic and electronic ballasts, making it easy for users to switch to LED lighting without having to replace their existing ballasts. This compatibility allows for a simplified installation process and minimizes the need for costly upgrades. Additionally, LED tubes have a longer lifespan and are more energy-efficient than traditional fluorescent tubes, resulting in lower maintenance costs and reduced energy consumption.