Copper is a toxin that is often used to kill algae in swimming pools or ponds. Here, I will focus on its use in ponds as I have discussed its use in pools here.
Since copper in solution is a blue color which tints the water, it gives an impression of purity. But it is only appearances. Maybe we could start thinking that green is clean. If your pond or pool can support algae the water is far less likely to mutagenize you and be toxic.
Copper is a toxic metal and even more importantly it is a phototoxin.
www.sciencedirect.com/science/article/pii/S0147651312002783
Phototoxins interact with light energy and transmit that energy in a harmful manner to living cells often killing them. If you add enough copper that it kills algae, it has a toxic effect on life, and almost certainly on you as well.
Dillute copper solutions and sunlight damage DNA extensively and cause cell death. I did my PhD work on this chemical reaction. And it is this reaction which is probably the reason copper kills algae. A copper solution in the absence of light has much less effect on DNA but is somewhat toxic. Solid metal copper is pretty safe for use in our water pipes.
If you are swimming in your pond, it is generally on a nice sunny day, not cloudy and overcast. Do you really want to be putting a _light activated_, DNA-damaging toxin in your pond water?
Copper ultimately, accumulates within the sediment layer and kills off a variety of beneficial life-forms such as:
1) insects and their larvae (dragonflys and damselflies — bees coming to drink).
2) crayfish and most of the other beneficial small aquatic arthropod ecology.
3) mollusks and other filter feeders. These would actually help keep the pond clear if they weren’t killed.
4) many, many beneficial bacteria and fungal populations.
The result of which is a damaged and weakened pond ecology.
Other points to consider:
1) Copper Sulfate has a short term effectiveness and is often misused and overused.
2) Copper remains in the pond and does not bio-degrade.
3) Copper is toxic to fish and other organisms.
4) Copper sulfate results in copper build up in pond sediments and creates a sterile bottom in the pond.
5) Copper can contribute to rebound blooms of problematic algae.
6) Copper sulfate is sold as a fine granular solid and its application is hazardous due to inhalation of dust particles.
7) If a heavy buildup of copper sulfate exists where dredging is to occur, the dredged materials may be considered by governmental agencies to be hazardous waste making disposal harder and more expensive.
The general reason copper and other algaecides kill algae is that _these chemicals are toxic_. And they are also toxic to you and your loved ones.
Bob