Unknown Larvae in Pool - Please help

[hydroengineerjoe]

Over the past couple of weeks I have been noticing these greyish whitish larvae caterpillar looking thing (for lack of a better word) in my swimming pool. I have tried shocking the pool a couple of times and it doesn't seem to kill them. They also seem to multiply quickly in the pool and are growing in number. Any idea what they are? How to get rid of them?

Please see picture.
http://www.daconta.us/Media/larvae.jpg

Although I am a pool novice, the pool water seems like it is in good condition according to the testing kit and I keep it clean regularly.

Any help would be appreciated. Thanks, Joe

[Denniswiseman]

If shocking didn't kill them then you may have to high a level of CYA which will render the chlorine in effective
How are you testing?
What form of chlorination are you using?
Can you post a set of numbers here
FC:
TC:
pH:
TA:
CH:
CYA:
Pool chemicals:

[hydroengineerjoe]

Thanks for the response. I am testing using a 'tht 6-way test kit'. For CYA test used 7 mL of pool water and 7mL of cyanuric acid reagent. Mix 30 seconds and then put in tube with black dot on bottom until can't see black dot. Test results showed in normal range (see below)

I went to Leslie Pools and the man there didn't know what the larvae was. Asked if my chlorine shock was powder and sold me liquid shock. Put a gallon in yesterday after I cleaned pool of about 40 of these larvae. Also cleaned pool filters. When I cleaned pool this morning, some appeared dead..others still alive. Only had about 5-10 in the pool that I believe I missed from cleaning yesterday. He said if not killed to come back in a few days and we will try a stronger chemical.

From your response I tested water this morning with the following results.

FC: - Kit doesn't test for it. When I went to Leslie this morning, same guy didn't even care about this test. Said TC is about the same as FC. This scares me as to the guy's knowledge of pool chemicals and testing.
TC: at least at 5 (maybe higher) as yellow color goes according to test equipment and this is the highest reading. But color seems pretty close to 5.
pH: - at least at 8.2 (maybe a little higher) as color goes according to test equipment and this is the highest reading. But color seems pretty close to 8.2.
TA: - 130 ppm
CH: - seems very low as test kit hardness indicator says that if present should turn water red and only turned it minimally yellow to orange. I was going to go to store and add hth calcium plus, but guy at Leslie pool store said this isn't a bid deal and it is good to not have high hardness.
CYA: - seems most important, levels indicated between 30-40 ppm. According to information this is in a good range for the pool.
Pool chemicals: I have been using hth pH decreasor, ultimate shock treatment and chlorine tablets. Leslie sold me Desert Formula liquid chlorinizor and I added a gallon yesterday.

[Denniswiseman]

First of all free chlorine is the available chlorine to sanitise your pool, combined chlorine is the used chlorine that needs to be removed
A CYA of 40 will require a Chlorine level between 5 and 7 with a shock level of 16 as in the Chlorine / CYA Chart
You need to reduce your pH and TA with muriatic acid as indicated here Pool Levels
Increase your CH as well as if there is insufficient it will draw from your plaster
To chlorinate, bleach (sodium hypochlorite) is best as it doesn't add any thing to the water or a SWCG
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
You really need to get a good test kit (Taylor K2006C or a TFT100)and don't trust the pool stores as they are in the business of selling
When you have the pool water balanced OK and determine your combined chlorine a Slam would be good and should kill of those bugs
I hope this helps you get on the right track to get your pool right

[hydroengineerjoe]

Thank you for the response. I will get the better test kit and get my water balanced and then try the SLAM.
Thanks for the help.
Sincerely, Joe