Pool Blanket + Algae And Green Pools


Active member
Oct 29, 2010
Temecula, CA

Thank you for taking the time to read my post. I will give my readings here

Pool gallons: 18,500
Pool Type: Plaster White
FC: 10+ ? (1 qt 25 fl oz of Sodium Hypochlorite 12% + 2 packets of Calcium Hypochlorite)
CC - Was A Lot
CH: In range
Phophates: 1000 ppb (will get to this)
TA: 100
CYA: 100 (above 90..bit high?)
pH: Not sure (but yesterday was 8.0+ (due to the liquid bleach) and probably much lower due to Granule packet shock....also added in muriatic acid - 24 fl Oz to bring it to 7.2....it's probably bordering on 7.2 now - will test later).

In any case, I'm use to keeping a pool clean for my folks. I've been doing it for 2 years now...but the fact is....I've gotten lazy. They bought a solar blanket cover (for these past summer heatwaves -living in an arid area) and I frankly stopped testing the water every day as recommended during summer by all you nice folks here.

Pool = Swamp green when the blanket was removed. Yay! So I basically have to be honest in saying I just put a ******** of chlorine and it made the pool beautiful last weekend. I then left the blanket on again this week...and Sunday Afternoon - Swamp Pool! :) Yay. In any case...I tested my water thoroughly...told myself no more Crud. And balanced my pH......probably lowered my TA from 100, to 90? 85ish due to pH.

Now the water is finally a blue color....I can see the bottom of the pool...it's a bit foamy right now....and cloudy. (Been like this since yesterday but got clearer). The pool people at the store told me to get rid of my high phosphate levels -----so I got PhosFree. Have not used it yet because I have some questions.....and any other advice you can all give me will be great....maybe I've been wrong in anything I've said so far.

1A. Is PhosFree necessary? A lot of people at havuz say its not, even if there are solids in the water...
1.Do I need to 'Air' out the pool when the blanket is on everyday?
2. I usually only run my pump on the day we swim...should I be running this everyday for like an hour or so? I read somewhere it should be everyday....I don't do this to save on electricity...but I find I spend an equal amount of money on chemicals either way? Lol.
3. Should I CLEAN out the filter which I cleaned just a month ago? The pool store people said to clean it out or the algae will come right back in the pool - a never ending cycle....but last I checked....if I do this - it'll just come back from spores in the air either way (and it's pretty darn windy here!)
4. I am guessing I will HAVE to clean out the filter if I want to REMOVE the phosphates from the pool with phosFree?
5. Why does a solar blanket make algae bloom INCREDIBLY fast. Usually I can leave the pool for a week without it becoming DARK DARK green....then again, I notice the chlorine LASTS longer too....

Any help would be appreciated on those 5 questions.

Melt In The Sun

TFP Expert
LifeTime Supporter
Oct 29, 2009
Tucson, AZ
CaptianJack, welcome to TFP! :wave:

Answers to your questions:
1A. No. It's not necessary, and a waste of money.
1. No, but a little breath of fresh air every few days is a good idea.
2. You should be running the pump every day for several hours. This keeps the water circulated and filtered and keeps the chlorine mixed in well. Generally the rule of thumb is one turnover per day, but it can be less in the winter if nobody's swimming.
3. You should clean the filter whenever your filter pressure is ~8 psi higher than your clean filter pressure. If you kill all the algae (more on that in a minute) it doesn't matter if all the dead bodies are in your filter, it won't grow back.
4. Correct, but phosphate removers are a waste of time.
5. It doesn't. Something else is going on.

Now, a few questions for you (and answers to questions you didn't ask):
- where are you located? Anyone swimming this time of year?
- how are you testing (strips, drop test, pool store, ...)? Your results sound like strip tests at the pool store, which are about as reliable as spinning the dial on the game of life.
- how do you normally chlorinate the pool (tabs/sticks, powder, SWCG, ...)?

Your CYA (stabilizer) level is especially important. It is too high according to your test results, and is likely even higher than that. You probably need to partially drain the pool to lower that level. Too much stabilizer reduces the effective chlorine level. After the CYA is at a reasonable level, you will need to shock the pool. This is not a one-time dose of chlorine, but a process that takes some time.

Everything is explained in detail in Pool School (link at the upper right of the page or in my sig). An hour or so spent reading will make your life much much easier.

You need a good test kit to really know what is going on with your water. The TF-100 is the best out there (linked in my sig). It is essentially the same as the Taylor K-2006, but with different reagent sizes and a lower price.

Well, I think that's enough blab for now from me :blah: . Take a read up in Pool School and post back any questions!