Frog mineral systems

[chem geek]

Presumably, copper is better at killing algae and silver does kill or inhibit the growth of some bacteria. Neither kill (deactivate) viruses. The idea that having a mineral system or an ozone or UV system require lower chlorine levels is only half-correct.

The reasoning is correct if talking about the total amount of chlorine needed IN RESERVE so that it doesn't get consumed too much and drop too low. The same thing could be said for having Borates or another algaecide in your pool.

The reasoning is incorrect if talking about the amount of chlorine needed to properly disinfect and kill bacteria and viruses. A certain minimum concentration is needed for this. So even if every single bug were killed in a perfect ozone or UV system (or SWG), you would still need a minimum chlorine level in the main body of the pool to kill bugs that stayed stuck to pool surfaces in biofilms and to kill them quickly before the water eventually makes it through the circulation system. [EDIT] If you brush the sides and bottom (all surfaces) of your pool regularly (weekly), then an ozone, UV or SWG system could probably be run at bare minimum disinfection levels and not experience algae -- users running 3 ppm FC and 80 ppm CYA seem to be in this category while other SWG users seem to require 5-6 ppm FC to avoid mustard/yellow algae. [END-EDIT]

Now in practice, it takes less chlorine to achieve a minimum disinfection level (corresponding roughly to 650 mV ORP or to 0.011 ppm hypochlorous acid) than it does to inhibit algae growth so in that sense one can indeed lower the chlorine level SOMEWHAT. So instead of needing a minimum of around 3.5 ppm FC at 30 ppm CYA to prevent algae (assuming 0.05 ppm HOCl is needed to prevent algae), you could have about 1.0 ppm instead (for 0.013 ppm HOCl), but this would be a bare minimum. Obviously, at higher CYA levels, more chlorine would be needed.

I agree with Carl that it's a waste of money -- not so much because it isn't effective, but because it is costly and has side effects (copper staining, mostly). Borates seem to have fewer problems and are not only an algaecide, but an additional pH buffer as well. If someone wants to spend money, then using PolyQuat 60% would be a better way to go and would accomplish much the same thing (PolyQuat 60% has some affect against bacteria as well, though it's better as an algae preventative and also as a clarifier).

Richard