Do I need a baby bath tub if I have a regular bathtub?

Not strictly. Several parents in r/moderatelygranolamoms and r/NewParents note you can bathe with the baby or use the sink. The main argument for a dedicated tub is water economy and back strain — a small tub uses much less water and lets you set the baby at counter height. Sling-style supports like the Angelcare are popular specifically for use inside an adult tub.