Algae over night ?

jetola

Member
Apr 27, 2020
16
Denmark
So i have a question.
My pool is an outdoor pool with metal-sides and a rubber bottom.
Over many weeks now i have maintained my pool every day. PH is 7,6 and Chlor is between 1,5 and 2. I use the phenol red and dpd1 tablets to Measure - and i measure every day and add chlor every day - to keep i close to 2.0 constantly. I add the chlor every night when pump starts.

every day i also vacuum the pool, so in the evening the pool stands razor Sharp. Totally clear water and no debree anywhere.

So at night it put on my summer cover and my pump runs for 8 hours (22:00 - 06:00) - and every morning i have several green/Brown spots on the bottom of my pool. I assume its algae because they are dust-like and easy to vacuum up with my catfish.

but why do they come - every night - when the pool is well balanced and its totally cleaned the evening before ?.. is it just How it is or is there something i Can do ?
 
Last edited:

jgofnj

Well-known member
May 28, 2013
206
Hillsborough, NJ
You have an Algae problem,. What is Chlor? Are you talking about the Tri-Chlor pucks? What you really need is to run a full test and look at your CYA, I bet it's way too high and you need to either lower your CYA levels or increase your Chlorine.
 

bmoreswim

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Jul 16, 2012
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I’m not familiar with the test kits available in Denmark. However, electronic testers for the consumer market are not particularly accurate and need calibrating very often. Think every week. You will be better served finding access to a kit to test the following. And specifically the FC test should be the FAS-DPD drop/color-changing test variety.

FC
CC
CH
TA
pH
CYA

The key as jgof alluded to is the FC/CYA Chart. FC/CYA relationship. It says that FC should be 7.5% of your CYA. Period. So a reading of 1 or 2 FC is meaningless without knowing your CYA level. Literally, it could be like you have no FC in your pool and be a breeding ground for algae other contaminants. Chemical companies don’t tend to recogncize the relationship. But it’s the cornerstone of trouble free pool care. ABCs of Pool Water Chemistry. What is TFPC? - Trouble Free Pool
 

jetola

Member
Apr 27, 2020
16
Denmark
I’m not familiar with the test kits available in Denmark. However, electronic testers for the consumer market are not particularly accurate and need calibrating very often. Think every week. You will be better served finding access to a kit to test the following. And specifically the FC test should be the FAS-DPD drop/color-changing test variety.

FC
CC
CH
TA
pH
CYA

The key as jgof alluded to is the FC/CYA Chart. FC/CYA relationship. It says that FC should be 7.5% of your CYA. Period. So a reading of 1 or 2 FC is meaningless without knowing your CYA level. Literally, it could be like you have no FC in your pool and be a breeding ground for algae other contaminants. Chemical companies don’t tend to recogncize the relationship. But it’s the cornerstone of trouble free pool care. ABCs of Pool Water Chemistry. What is TFPC? - Trouble Free Pool
You were spot on. Now i bought the poollab 1.0 tester, and a test showed

PH: 7,7
FC : 1,22
TC: 1,28
TA : 118
CYA : 6

So - my CYA is way too low, which is probably why my chlorine wanish Way too fast - and thus algae in the morning.

i Will add some CYA (stabilizer) to protect the chlorine -lower the PH a bit - and keep the algae away 👍🏻
 
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