Aquarium Co-Op Test Strips, Chlorine, and the Sun

[Bec]

So I've been setting up a mini pond this summer for the first time and I've had one set up since 4/21/22. I always dechlorinated the water when I topped off but I was getting really thrown off by these chlorine readings I was getting on the test strips. It seems like I would still get chlorine even when I hadn't topped off with any water but rain water in weeks. After searching the forum for people running into similar issues, I initially thought the container I was using (a resin planted from Home Depot) was leaching chlorine. So I completely changed over the substrate, sponge filter, and plants to a new container which was actually a used black water trough container I bought from someone who had used it heavily for farm animals. 

After filling the new container up and dechlorinating, I took a reading and again a high amount of chlorine. I dechlorinated a second time and tested again the next day, again more chlorine. I finally realized that both containers could not be leaching chlorine. So, today I performed the following test and got some surprising results. 

I did the following:

1) Dipped the test strip into the dechlorinated pond and took it inside immediately for reading

2) Took a water sample from the dechlorinated pond inside and then dipped the test strip in it

3) Dipped the test strip into the dechlorinated pond and left it outside in full view of the sun

My results were as follows (see attached image)

1) No chlorine

2) No chlorine

3) At least 3.0 ppm chlorine

The experiment wasn't perfect but the only variable I changed was the sun exposure on the test strip. I wanted to test my inside tap water to see if the sun was really causing these high chlorine readings. So I dipped a new test strip into a sample of my inside tap water (dechlorinated) and then put it outside in full view of the sun before I read it. I ended up getting more than 3.0 ppm chlorine. 

I wasn't aware that UV light or the sun would effect test strips like this and a lot of other kits don't even include chlorine so I thought this was interesting to share. Especially with so many of us setting up summer tubs right now! 

[Wrencher_Scott]

Nice ,thanks for that.

I use a swimming pool chlorine test (drops) before I add my water just to be sure.

[Bec]

Yeah of course, I'm happy to share with the community! The kicker was me just testing my 10 gallon (which has been set up for almost 2 years) now and then leaving the test strip outside in the sun and getting a chlorine reading. I'm not super versed on the science behind the UV rays and the chlorine test pad but good to know for the future! 

[Brian]

Wow..  I would not think that would make a difference…

[Bec]

Also here's the test strip reading of my inside 10 gallon aquarium that has been set up for almost 2 years. I dipped the test strip and then let it sit outside in the sun before reading. Pretty wild but I'm super happy that this confirms the false reading. 

 

[nabokovfan87]

On 5/26/2022 at 11:23 AM, Bec said:

The experiment wasn't perfect but the only variable I changed was the sun exposure on the test strip. I wanted to test my inside tap water to see if the sun was really causing these high chlorine readings. So I dipped a new test strip into a sample of my inside tap water (dechlorinated) and then put it outside in full view of the sun before I read it. I ended up getting more than 3.0 ppm chlorine. 

I wasn't aware that UV light or the sun would effect test strips like this and a lot of other kits don't even include chlorine so I thought this was interesting to share. Especially with so many of us setting up summer tubs right now! 

When you let the strip sit, how is it sitting?
 

 

On 5/26/2022 at 12:37 PM, Bec said:

Also here's the test strip reading of my inside 10 gallon aquarium that has been set up for almost 2 years. I dipped the test strip and then let it sit outside in the sun before reading. Pretty wild but I'm super happy that this confirms the false reading. 

very very very interesting stuff!

Also, Welcome!

Edited May 27, 2022 by nabokovfan87
added video

[Hobbit]

Ohhhhhhhhh! I had this issue last year (and this year) and this is a really interesting discovery! I’ll have to try the experiment myself.

[Phillip]

On 5/26/2022 at 1:23 PM, Bec said:

So I've been setting up a mini pond this summer for the first time and I've had one set up since 4/21/22. I always dechlorinated the water when I topped off but I was getting really thrown off by these chlorine readings I was getting on the test strips. It seems like I would still get chlorine even when I hadn't topped off with any water but rain water in weeks. After searching the forum for people running into similar issues, I initially thought the container I was using (a resin planted from Home Depot) was leaching chlorine. So I completely changed over the substrate, sponge filter, and plants to a new container which was actually a used black water trough container I bought from someone who had used it heavily for farm animals. 

After filling the new container up and dechlorinating, I took a reading and again a high amount of chlorine. I dechlorinated a second time and tested again the next day, again more chlorine. I finally realized that both containers could not be leaching chlorine. So, today I performed the following test and got some surprising results. 

I did the following:

1) Dipped the test strip into the dechlorinated pond and took it inside immediately for reading

2) Took a water sample from the dechlorinated pond inside and then dipped the test strip in it

3) Dipped the test strip into the dechlorinated pond and left it outside in full view of the sun

My results were as follows (see attached image)

1) No chlorine

2) No chlorine

3) At least 3.0 ppm chlorine

The experiment wasn't perfect but the only variable I changed was the sun exposure on the test strip. I wanted to test my inside tap water to see if the sun was really causing these high chlorine readings. So I dipped a new test strip into a sample of my inside tap water (dechlorinated) and then put it outside in full view of the sun before I read it. I ended up getting more than 3.0 ppm chlorine. 

I wasn't aware that UV light or the sun would effect test strips like this and a lot of other kits don't even include chlorine so I thought this was interesting to share. Especially with so many of us setting up summer tubs right now! 

Wow! I’m going to try this tomorrow. I’ve been getting similar results on my outside tubs and I’ve been stumped! Couldn’t figure out why I was picking up chlorine. 

[Torrey]

You just answered why my patio tubs didn't ever register chlorine... We are on the north side of the building, so only get sun for a couple of hours in the early morning and late afternoon, and that is only during the summer. Tomorrow I'll test in the sun, and then call my daughter and let her know her tubs probably don't have chlorine in them, lol