I decided that the most effective way of removing the slugs was to use the saltwater solution inside the tub. By dousing the tub with a salt solution, the water is diluted enough that it will not kill the slugs, but encourage them out. Because my hot tub isn't running, my plan is to just spritz the solution along the sides (top to bottom) as well as bases of the tub and see if the slugs go away, without harming them.
STEPS:
1. count and record number of slugs in the hot tub 2. make a salt water solution using 24 oz of water and 4.5 tsps of salt 3. put solution into a spray bottle 4. spritz saline solution along all the interior "walls" and bases of hot tub (morning) 5. At the end of the day, record the number of slugs inside the hot tub 6. Repeat steps 4-5 each day for 7 days 7. After 7 days of collecting data, record the average number of slugs throughout the week