Beyond frustrated with algae

[edodds]

I am beyond frustrated with my green pool. I opened my pool 1 week ago and as usual it was green with algae. Usually I use the standard pool opening kit, shock, brush vacuum and I am good to go. I followed the same proceedure this year but I just can't get rid of the algae. I have shocked the pool with leslies fresh and clear 4 lbs, regular shock, and power powder with a total of probably 10 to 12 lbs by now. I have tried algae treatments twice and still it is there. I have taken my DE filter apart and cleaned the fins and it still doesn't help.

Normal chlorine is 3" tablets

PH 7.4
TA- 110
FC- .5
TC-1.5
CA-110

Any help would be so appreciated.

[mas985]

Plain old bleach (liquid chlorine) is far more effective at killing algae. Try following these instructions and you will see it disappear.

Defeating Algae

[AllenGMyerson]

The problem is your cyanuric acid level, which is probably much higher than 110 ppm. You need to stop using tabs and lower your cyanuric acid level. You need to raise your free chlorine to 40 % of your cyanuric acid level to kill algae. You need to keep the chlorine level at 40 % of the cyanuric acid level until all of the algae is completely gone.

[SPMG]

Hello,

Further to the previous replies - Algae cannot proliferate without there being phosphates in the water.

Phosphates in your pool water are bad news. Orthophosphate is the major algae-food in pools. Algae need just a few basics to proliferate - food, light and water. If you’re an alga spore, the light and water are pretty easy to come by in a swimming pool but food is the tricky one. Restrict the food supply and algae will find it much more difficult to grow. Nitrogen and carbon are also important factors for the growth of algae but studies prove that the key ingredient is phosphate.
Complex phosphates get into your pool as a component of sweat, as orthophosphate added to the mains supply by the water companies to control scaling and corrosion in metal pipework (in UK but perhaps not so often elsewhere), in airborne fertiliser (bird-poo) and as a component of the vegetable matter that blows into your pool, including algae spores.

Some wells in intensively farmed areas contain phosphate as a run-off from fertilisers. Complex phosphate breaks down in water, through oxidation and hydrolysis, to form orthophosphate. If you have phosphates in the water you will almost certainly get algae if at some point your chlorine level drops below optimum 1-3 ppm (for example if a child urinates in the pool) - if you have algae already there is definitely phosphate in the water. As algae needs phosphate to exist, algae itself is rich in phosphate. Chlorine will kill the algae but then the phosphate is released back into the water ready for the next algae attack and the vicious circle continues.

Removal of the phosphate is the best solution. By replacing half the pool-water, something that ought to be done every couple of years at the least, and topping up from a phosphate free source you will halve the phosphates (and the built-up cyanuric acid) in your pool. Chemical removal of phosphate is done by using aluminium compounds or lanthanum compounds. Aluminium can strip phosphates down to about 500 parts-per-billion (ppb) but to achieve the ideal of under 100 ppb lanthanum carbonate must be used. Applied via the skimmer, these compounds sit on the sand as crystals and slowly dissolve to coat the sand in a layer of phosphate-hungry lanthanum carbonate and lanthanum phosphate. This effectively removes the phosphates from the pool water and locks them away.
Remember to carry out a filter backwash BEFORE applying lanthanum compounds, or you may flush them to waste before they have had a chance to dissolve.

You'll find the answers to 99% of your pool questions here

Good luck

SPMG

[mas985]

Here is what Chemgeek has to say about phosphates in this post:

Phosphate Levels and Algae Control by Chlorine
There is a myth of not being able to control algae by chlorine alone and that high phosphate levels must be lowered. Though phosphate levels do influence the rate of algae growth, phosphate removers only lower orthophosphate, not organic phosphates, so may not always completely stop algae growth and nitrates are also a limiting growth factor. Phosphate removers should be seen in the same vein as algicides that inhibit algae, but may not prevent it completely. Chlorine alone can be used to control algae if the FC/CYA ratio is above minimum levels (see chlorine/CYA chart described above).

The handbook does not promote the use of phosphate removers, though does note that phosphates and nitrates are nutrients required for algae growth, but also notes the many different sources of phosphates (including storage in algae themselves). Various algicides are discussed with various pros and cons. The handbook notes that routine superchlorination and the use of an algicide on a maintenance basis are useful tools in the prevention of algae. However, there is no discussion of how chlorine alone, using a sufficient FC/CYA ratio, can prevent algae growth, though it is noted that it is very important that disinfectant residuals be maintained at all times to prevent the growth of algae.