Copper as algecide


New member
Mar 15, 2021
Country NSW Australia
Hi Ive just started using Cu as my algae treatment. We chlorinate before swimming.No CYA in water. I test for cu using a Microtest kit for copper.
My initial dose was 4 heaped teaspoons cu.We calculated that to be 20 g in 14000 us gallons.I have added perhaps 10 teaspoons cu in total in last 3 months since we started the cu program
Result says .2 mg/l. Is a low reading but pool is clear?
We've just had 5 inches rain in last 2 months
After a rainfall event I add a heaped teaspoon of technical grade cu I bought off the interweb. The label states its 98% pure. I assume that a heaped teaspoon is 5 grams
Is .2 ppm cu enough as an algaecide? ( it seems to be or the test kit is inaccurate )
Cheers from Australia


Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
Franklin, NC
No matter how much rain you have the copper does not go away. Some will be splashed out, but I'm betting almost all of what you have added is still there.

I'm not sure what you mean by "We chlorinate before swimming.", but without residual chlorine in the water all the time yu really don't have sanitary water.


Bronze Supporter
Mar 5, 2020
Melbourne, Australia
Pool Size
Salt Water Generator
SWG Type
Astral VX 7T
We do not recommend the use of copper based algaecides. You want to keep any metals out of your water, as they will cause staining eventually.

We actually don't recommend any algaecides. There are some indications, like preparation for closing a pool over winter, where Polyquat based algaecides can make sense. Otherwise we rely on chlorine, it does a marvelous job at killing algae.

TFP does a few things different to the "traditional" pool industry, have a look through TFP's Pool School to get an idea about the approach being taught here:

Particularly the FC/CYA-Chart, which is one of the cornerstones of TFP:

You need a constant residual of chlorine to ensure that bacteria, viruses, etc, are constantly kept at bay. Just adding chlorine before swimming does not guarantee safe water.

Here is a good summary article about metals in pool water:
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