Many times when people have a jacuzzi tub they will use it for a while and then the fun of it starts to wear off and they won't be using it quite as much. Or they will move into a house that has one that hasn't been used in a while. When this happens, many times scum and other junk can start to develop in the jets of the tub. This scum is often times only visible when you turn the tub's jets on and make the water look awful. Fortunately there is something that you can do about it.
Fill your tub with hot water. You will want it to be at least a couple of inches above the jets, otherwise your jacuzzi will not be cleaned properly.
Measure out a half cup of bleach and a tablespoon of detergent and put it in the Jacuzzi tub.
Run the jets on their highest setting and fully open the jets. This will offer the most amount of water movement in the tub and also the maximum amount of water (and thus cleaner) running through the jets.
Watch the Jacuzzi tub run for about 15 minutes. You should see a lot of dirty water and scum floating around in the tub at this point.
Drain the tub and clean out any remaining junk from the walls and floor. You can simply use paper towels or a rag to clean up this mess. Don't worry about getting every little thing out, just the larger pieces that will have a difficult time going down the drain.
Refill the Jacuzzi tub; again, above the jets.
Run the tub at full blast for another 10 minutes to rinse out all of the remaining dirt and bleach. If you notice a lot of junk still coming out of the jets, you may want to repeat the whole process or at least rinse it again until the jets spray clean water.
Maintain the clean jets by spraying with bleach at least once a week and cleaning them out with a jacuzzi cotton swab.