Swimming Pool Stains & Metal Ions: Copper, Silver, Iron & More, II

Copper and silver ion based swimming pool algicides

The earliest use of silver and copper ion swimming pool treatment was not as a sanitizer, but as an algicide.

Pool service techs have apparently been using silver nitrate and copper sufate, alone and in combination with other materials, for as long as there have been pool service techs.

I have to say, I have no personal experience with using silver -- I have never even seen a bottle of silver solution for sale, except in a catalog or online! I have read, and I have been told, that (1) silver is very effective and (2) it can cause nasty black (silver chloride) stains. I can also tell you that silver algicides are expensive, and are still available. Click this link to search Google: http://www.google.com/search?q=silver+algicide

What I found most interesting about the listings, is that almost all the top listing mentioned the necessity to be very careful to avoid stains. If you understand how much sales and marketing types dislike including a warning in the first few lines of their sales pitch, you'll grasp how severe the staining problem from these algicides really is!

So, if you want to (a) get rid of your algae and (b) stain your pool gray or black at the same time, silver is a good way to go! Seriously, if you don't mind the stains, since they are silver based, they are likely to inhibit future algae growth.

On the other hand, copper algicides are everywhere. They are available as pure copper sulfate, either granular or in water solution, or blended with stain control agents or foamy algicides.

I have used copper algicides.

I'm not impressed.

They seem to kill algae, but not all that quickly. Chlorine is MUCH faster, and almost always cheaper. But copper algicides don't just seem to cause stains: they absolutely do cause stains. And, it doesn't take much, either.

There's also something really odd going on with the blending. Copper ions are, naturally, most effective when they are tied up with some other compound, but are 'free' and ready to go to work against plant cells. But, when you blend them with something like triethanolamine, a "chelant", then the copper is not longer 'free' to act.

I've not been able to find any actual studies comparing unchelated copper products, with chelated ones. So, I don't know for sure: but I suspect that we've run into the same "Catch 22" mentioned before. If you have enough 'free' copper to be effective, you have enough to stain. And, if you make sure stains don't occur, well then you don't have enough 'free' copper to do the job.

Metal ion based swimming pool treatment: the bottom line

The bottom line is simple, again: if you want to stain your pool, either copper or silver algaecides are a good way to do so. But, if you want to kill algae without messing up your pool chlorine, bromine or polyquat algaecides are a better choice. All in all, just plain old chlorine is your best choice!