Simply Place in pump basket or skimmer basket. Eliminates all types of algae. Reduces chemicals. Effective for up to 6 months. Simplifies pool and spa Care. The for Sundance Spa’s Unit supports 400 – 1000 gallon spa’s or fountains. is an easy to use algaecide that reduces chemical demand, improves water quality, lasts for up to 6 months, and really works! contains a proprietary blend of minerals that continuously and effectively eliminates algae. Simply start with fresh water and a clean filter and pick the correct sized Spa unit based on total gallons, then, drop the for Spa unit into the pump basket or skimmer. Or for Sundance Spa’s, place the Unit in the skimmer door slot.