Are Phosphates Really a Problem?
“Phosphates” is a trendy word in the pool industry these days. Some pool companies argue that this is the new buzz word, and it’s pointless to be concerned, but many realize that treating for phosphates in a pool is an important step in proper water chemistry.
In a pool that is well maintained, there is usually no benefit from using algaecides or phosphate removers. However, if a pool is not well maintained, then there can be a significant benefit to using a polyquat algaecide and to limiting phosphates to less than 50 ppb (parts per billion) or nitrates to less than 10 ppm (parts per million). If nitrate levels exceed 25 ppm then they need to be reduced by dilution with water that is low in nitrates.
If the chlorine levels will not be kept at a consistent level sufficient to prevent algae, then supplemental methods need to be employed to prevent algae.
Algae need both nitrates and phosphates to proliferate. If either nutrient is sufficiently limited, then the algae will be effectively suppressed. Most fertilizers contain nitrogen, phosphorus, and potassium, three essential nutrients to plant growth. Orthophosphate (also known as free orthophosphate) is the primary form of phosphate used by algae. One of the primary sources of phosphates in pool water come from phosphonate based (organic phosphates) scale and stains inhibitor products.
Limiting phosphates will provide an extra measure of algae prevention when chlorine levels go below the required concentrations to prevent algae.
I think that if someone is going to have a pool it should be well maintained. It should be kept cleaned, filtered and chemically balanced. While limiting phosphates can help suppress algae, it does not insure a clean and safe pool. Bacteria and viruses can still be present due to low chlorine, and poor chemical balance can cause swimmer discomfort and it can damage pool surfaces and equipment.
Adding borates can help suppress algae and they also help buffer the pH. The borate products work, in part, by lowering the levels of carbon dioxide in the pool water (At least that’s what some claim). Carbon dioxide is essential for algae growth. The lower levels of carbon dioxide also slow pH rise from salt chlorinators that cause pH rise partially from aeration.