Why sweat it with BBB and a tub to save, literally, pennies. Buy some bromine and a floater and be done with it. $20 for bromine lasts me six months. Borax if you need to bump up the ph and dry acid ($3 or $4 for a bottle that's lasted well over six months) to bring it down. Hut tub maintenance is very, very cheap, compared to a pool, and I really don't see where any big savings can be had. MHO