Fighting Algae with Borax

[chem geek]

Sumo1,

PolyQuat 60 has no metals in it. I forgot to list copper as an algaecide in my list of ways to keep away algae. Copper is a very effective algaecide, not only for preventing algae, but also for killing existing algae, BUT it comes with serious side effects of precipitating out as blue-green copper hydroxide at high pH causing water to turn greenish (and can stain plaster, too) and also can make blond hair turn green. There are also linear quats as an algaecide, but those tend to foam with aeration so is why we generally only suggest maintaining chlorine levels to keep away algae or using PolyQuat 60 in small amounts mostly as insurance (for prevention, not for getting rid of an existing bloom).

PolyQuat 60 is just a long polymer (which just means a very long molecule with repeating subunits) whose key chemical factor is a nitrogen that carries an extra positive charge with it. So you can imagine this long string of a molecule that has positive charges strung along it sort of like Christmas lights. Most cells, including algae cells, have a negative surface charge so the PolyQuat is attracted to them and will tend to clump them together (in this sense, PolyQuat is also a clarifier and was originally sold as such until it was seen as more profitable to sell it as an algaecide -- it's really both). When attached to the algae cells, the large molecule tends to block the ion channels preventing the cells from getting nutrients (positive charged ions, including phosphates, nitrates and carbonates) from the water. It also has some disinfection capability against bacteria that works in the same manner, but because this process is slow-acting it cannot be used alone (i.e. chlorine is still required) and it does not inactivate (oxidize) viruses.

There should be no problem using PolyQuat in a pool with an SWG.

Richard

[aylad]

When attached to the algae cells, the large molecule tends to block the ion channels preventing the cells from getting nutrients (positive charged ions, including phosphates, nitrates and carbonates) from the water. Richard

Seems to be one more reason to avoid the phosphate removers?

Janet

[waterbear]

Seems to be one more reason to avoid the phosphate removers?

Janet

Not really since phosphate removers remove phosphates and eliminate ONE of the sources of algae nutrition. There are still carbonates and possibly nitrates in the water that the algae can feed on. THAT is the reason that phosphate removers are not really necessary.

[chem geek]

I may be wrong about this, but I believe that nitrogen and phosphorous are both required nutrients -- it's not an "or" relationship. This link describes some of the nutrient requirements and this link talks more about the N:P ratio and how a lower ratio can lead to algal blooms and this link refers to N-limited vs. P-limited algal growth with the strong implication that both nutrients are required (i.e. both nitrates and orthophosphates). I've read other info that's consistent with this. I think the only either/or situation was between phosphorous and silicon for some species of algae that could or do use silicon instead of phosphorous. You'll also find C:N:P ratio data that adds carbonates to the mix, but again it's not an "or" relationship but an "and" relationship (i.e. all are required nutrients so eliminating any of them will eliminate algal growth).

We can't obviously eliminate carbonates from the water since it's exposed to carbon dioxide in the air and we want a pH buffer and calcium carbonate saturation. Ammonia may be present as a source of nitrogen, but only if chlorine is not present (since monochloramine occurs very, very quickly), but monochloramine would be taken up as algae food and would then kill the algae. So realistically it is nitrates that would be a source of nitrogen for algae. Typically the nitrates and phosphorous would both get into pools from fertilizer (i.e. blown soil), but nitrates can also come from the oxidation of organics (where nitrates are produced instead of nitrogen gas) and nitrogen gas itself can combine with oxygen and water to form nitrates (this is actually slightly thermodynamically favored and were it not for living organisms doing denitrification, biosynthesis and nitrogen fixation, the oceans would be 0.1 Molar HNO3).

Richard

[heymom1]

When you add the borax and muriatic acid, is it a one-time application? Or do you have to keep going back and fiddling with it? We've gotten rid of our mustard algae (but it rained again today) with high CL levels consistently, and now it's either time to start adding Polyquat or go the Borax way. I need easy. I will tell you that I don't like dealing with muriatic acid, I just don't - chemicals that smoke as you open them scare me. So if the borax is a one-time application (per season) I can go that way, or do the Polyquat.

Recommendations?

[chem geek]

The Borax + Acid is one-time except for small additions to compensate for dilution (splash-out, backwashing, rain overflow, etc.).

[waterbear]

If you initially add 50 ppm just monitor it and when it drops to 30 ppm bump it back up to 50 ppm.

[jhm]

It wasn't me, it was the borax!

Someone in another thread expressed concern about dogs drinking pool water with a high borax level. Any truth to that? I don't think I can keep my dog from drinking the water, but I read your whole other thread and the borax looks like it will kill two birds with one stone for me.

Thanks!

[Tredge]

Chemgeek had shown that borax at 50ppm is really no more 'toxic' than chlorine at normal levels. (At least thats how I read it).

Anyways....my dog drinks out of the pool regularly and shes very healthy. The way I see it that water is the cleanest she'll ever drink.

Most dogs can handle far more toxins than humans can due to their exceptionally large livers.

[jhm]

Chemgeek had shown that borax at 50ppm is really no more 'toxic' than chlorine at normal levels...

Awesome! Time to pack in the Mule Team.