pH mysteriously increasing

[andieb]

Hi everyone, 

The pH in my new 12 gallon long is mysteriously increasing and I don't know why.

I set up the tank 2 weeks ago, and used a sponge filter from an established tank. 1 week ago I tested all the parameters. There was ~20 ppm nitrate, no ammonia or nitrite.  However, the pH was off the charts, I had to switch to the high range pH test, and even that was off the charts too 8.8+ pH! I had a couple limestone rocks in the tank, which I took out, because I figured they were likely the cause. Then I did a massive water change, after which the pH was 7.5. Last Friday the pH had risen slightly, however now (the following Tuesday) the pH is back to 8.4! 

I can't figure out what's increasing the pH. 

Here's everything that's in the tank:

• CaribSea Supernaturals Crystal River - website states that it's inert, I use it in all my tanks and have never seen pH change. 
• Drift wood - should be lowering the pH if anything 
• Dragon stone - which is supposedly inert 
• Plants - dwarf water lily, dwarf sagittaria, marsilea crenata, buce, annubias, a pothos growing hydroponically. 
• And sooo much algae!

My leading theory is that the pH is being affected by the algae in the tank. Shortly after setting it up, there was a HUGE green algae bloom. The tank sits in front of a window and it also had a light which was on for 12 hours per day (I really wanted to make a carpet and I think I got a little carried away)... anyway, I've turned off the light (light is just on now for sake of the picture below) and plan to put a frosted glass sticker on the back of the tank to block some of the sunlight. I read somewhere that under high light conditions algae can cause pH to rise because its photosynthesis removes CO2 from the water. I'm wondering if that would be enough to explain the crazy high pH in the tank. Some additional evidence for this is that I tested the nitrates, nitrites, and ammonia today as well, and they were all completely zero.. probably because there is no bioload in the tank and the algae is removing it all. 

Wondering if anyone has any other ideas or factors I haven't considered. 

Thanks for your help! 

Here's pictures of when I first set it up and the algae monstrosity it has become...

[Fish Folk]

My best guess is that the high light level that supports algae growth, is conspiring to absorb all of your available CO2, thus raising pH. You could try adding a passive CO2 setup -- an inverted turbidity column, or similar (ca. 100 ml). You fill daily with CO2 from a Soda-Stream system, or similar.

I recognize it's tedious . . . and a bit of a kid's science fair show . . . but my son explains this in a video here. Go to timestamp 5:10...

 

[Galabar]

It looks like you might be getting a lot of direct sunlight on that tank?  Maybe that top line represents the top of the light streaming through the window?

 

[andieb]

Thanks for sharing that video, very informative, and what a beautiful tank! The DIY CO2 set up is ingenious! 

[RennjiDK]

Gas exchange is the primary driving force of ph in aquariums. Algae, especially cyano, can raise it dramatically, but that's in enclosed environments. That amount of green algae probably will gove you a ph bump, but it will be less than 1. Are you running an air pump next to that window? Do you have a lot of fresh air around the tank? The other issue is using an api kit for testing ph. I would personally look for a pen style probe, which can be calibrated before use.

[andieb]

Hi @RennjiDK, thanks for your response and suggestion. I use an API Test Kit. I haven't invested in a pH probe, since I figured they'd be expensive and I only have a couple tanks so don't mind taking the time to do a liquid test. Do you find the API liquid tests inaccurate? And yes, I'm running an air pump next to the window for the sponge filter. There is an AC vent above the tank so it should be getting decent air circulation, also because the lid leaves a pretty large opening. 

I tested pH again today and it was was at 7.4, so a big improvement. I taped some paper to the back of the tank to reduce the sunlight and I scraped off all the algae and did a deep clean and big water change. 

[RennjiDK]

On 8/12/2023 at 5:30 PM, andieb said:

Hi @RennjiDK, thanks for your response and suggestion. I use an API Test Kit. I haven't invested in a pH probe, since I figured they'd be expensive and I only have a couple tanks so don't mind taking the time to do a liquid test. Do you find the API liquid tests inaccurate? And yes, I'm running an air pump next to the window for the sponge filter. There is an AC vent above the tank so it should be getting decent air circulation, also because the lid leaves a pretty large opening. 

I tested pH again today and it was was at 7.4, so a big improvement. I taped some paper to the back of the tank to reduce the sunlight and I scraped off all the algae and did a deep clean and big water change. 

Api tests are pretty accurate, however, it can be difficult to interpret the results which is why it's always better to have a digital display. For instance, I cannot tell a difference between 40ppm and 80ppm of No3 using the api test. I know that my No3 is 11.2ppm when my egg checker tells me it is, +/- 0.1ppm.

Diffusing outside air directly into the tank will definitely bump it up significantly, as would adding a Co2 reactor in the line.

You will normally see a fluctuation of +/- 1 unit throughout the day, based on the levels of Co2 in the room with the tank.

[Galabar]

The tank looks nice. 🙂

 

[andieb]

@Galabar Thanks so much! 

@RennjiDK I agree that the tubes can be hard to interpret, and if you require precision then something with a digital read out would be better. I just know if my Nitrate reading is more orangey than yellowy, it's time for a water change. At least the ammonia and nitrite are pretty cut and dry.