Copper Ammmonium Complex For Algae

[jetskiron]

Can I use copper ammonium complex as an algaecide in my inground swimming pool in place of copper sulphate pentahydrate? And if so, would I use it in the same concentration?

[chem geek]

The copper ammonium complex will require more chlorine because the ammonium will combine with chlorine to form monochloramine. With additional chlorine, this will oxidize this monochloramine. So this is most likely more usable to kill existing algae when your Cyanuric Acid (CYA) is too high -- it's not really useful for maintenance.

Also, with either product you are adding copper to your pool and since you can't readily control the copper level unless you are testing for it you can get staining and blonds can get greenish hair. Staining can especially occur if the pH rises such as from shocking with a hypochlorite source of chlorine. If you have a vinyl pool you are at less risk, but if you have a plaster or fiberglass pool then staining is more likely and very expensive to treat.

I presume the reason you are using an algicide is that you are using Trichlor pucks/tabs as your primary source of chlorine. For every 10 ppm FC added by Trichlor, it also increases CYA by 6 ppm. So even with a low 1 ppm FC per day chlorine usage/consumption, continued use of Trichlor increases CYA by over 100 ppm in 6 months if you don't have any water dilution (if there are no rains with overflow and you have a cartridge filter so no backwashing).

You can prevent algae from growing by simply maintaining an appropriate Free Chlorine (FC) level relative to the Cyanuric Acid (CYA) level. You can read more about this at the Pool School.

[jetskiron]

Thanks so much for your help. So should I switch from the 3" Leslies chlorine tablets to a liquid chlorine in the gallon jugs?

My pool is 20 years old and until a few years ago, I always had to add muriatic acid to balance the ph. But then I had to start adding the soda ash instead if acid. I also went from 1 hopper of chlorine when the pool was new, to 3 hoppers and could never get the pool completely algae free. It still had the green algae in the scratches in the plaster (from dog clawing I think) and the Kreepy Krauley had algae I could never get off. I was brushing the pool every day about 20 minutes.

Then I tried a quart (half the recommended amount for my pool size) of the HTH Algae Free (Copper Sulphate) from Wallmart and within a week, there was not a trace of green algae anywhere. The pool was cleaner than it had been in years. And it stayed that way for a couple months, and with only 1 chlorine tablet hopper.

Then in the space of a week, the algae came back like crazy. I think I failed to keep the hopper full and the copper was about at its end anyway? So this is why I wanted to continue the copper treatment. The label on the bottle also said to continue with 16 oz/10,000 gallons of water every 3 months. I have not had the staining, and had been real happy with the algae being gone. But now you say don't use the copper algaecide. So I'm lost now.

I will follow the Pool School link you provided.

Thanks again

[chem geek]

It's your pool and you can do what you want with it. Copper will kill algae. What you described is completely typical of Trichlor users. At first, everything seems fine but over time (as the CYA level builds up) the chlorine becomes less effective and then more chlorine is needed (i.e. more tabs) until eventually algae starts to show. Using a copper algaecide works at first, but over time if you don't maintain the copper level algae can come back -- even if you did maintain the level algae could still grow if the CYA continues to climb high enough. There is a point where with enough water dilution you can keep the CYA in check and with the copper you can prevent algae, but the active chlorine level will still be low and oxidation will be slow so your pool won't necessarily remain crystal clear without shocking.

If you switch to using chlorinating liquid or bleach, then you don't have these problems, BUT you need to add chlorine every day or two. It's a tradeoff of convenience. There are other alternatives such as a saltwater chlorine generator (SWG) or a chlorine dosing system to make things more convenient, but these cost extra. You should read up and decide what is best for you.

[jetskiron]

Thanks much. You explain it very clearly. Then is there a way to reduce the CYA without draining the pool and refilling?

[chem geek]

No, the only practical way to reduce CYA is by dilution with water that has no CYA (such as fill water). You can do a partial drain/refill or multiple partial drain/refills or even a continuous drain/refill, but usually do not need to replace all of the water in the pool.