Swimming pool owners have several options available when it comes to maintaining a clean and sanitary pool. One of those options is the use of salt water rather than standard fresh water. Saltwater pools have about the same salinity as teardrops, meaning they're comfortable to swim in. They can become contaminated by algae, though, just like any body of water. When that occurs, use an algaecide--with certain provisions.
Algaecides are formulated to kill off algae, which are microscopically small plants that come in a variety of colors. Green, yellow and black are the three most common algae found in pools. There are also three major types of algaecide used in pools. The first group includes metallic (copper or silver) algaecides. The second group comprises quaternary algaecides, while the last group is composed of polyquat algaecides, which are expensive but effective against green, black and yellow algae.
Because of the nature of salt water, metallic algaecides are not recommended. Copper and silver react with salt water and will leave stains on a pool's walls. Metals can also damage a saltwater pool's salt cell chlorinator, which is responsible for disinfecting the pool. Fortunately, both quaternary and polyquat algaecides are safe for use in saltwater pools.
Saltwater pool-friendly quaternary, or "quat," algaecides have the advantage of being low cost in comparison to polyquat algaecides. They're also widely available in a variety of formulations and sizes. Their disadvantage is that they'll reduce available chlorine in a saltwater pool, meaning more will have to be added. Plus, quats are only effective for about 24 hours.
Polyquat algaecides, powerful algae killers, are also saltwater pool-friendly, effective at clarifying pool water and don't reduce chlorine levels. No additional chlorine will need to be added after treating a saltwater pool, which can save money. Their downside, other than expense, is that they're effective for only one to two weeks after being added to salt water.
The best means of controlling algae in a saltwater pool is to prevent its appearance in the first place. Maintain proper salt levels along with stabilizer chemicals. Cyanuric acid (CA) is the most common of such chemicals, and it needs to be 60 to 80 parts per million (ppm) in a saltwater pool. If using an algaecide, however, follow all instructions carefully and monitor levels, using a saltwater pool test kit.