What's the lowest acceptable pH for a mixed reef tank?

[Ed Chan]

Asking because I just started my treatment of Flux Rx to address GHA and in doing so, have to turn off my skimmer. Normally I have my CO2 scrubber attached to the skimmer which gets my pH to fall within 8.00 and 8.25.

My first night without the CO2 scrubber running and right now I'm at a low of 7.79

Fish seem fine so far, and I know that generally my tanks pH reaches its low point now (11am PST) and raises or peaks closer to midnight.

Should I be concerned if my pH drops to this level? What would the negative effects be on both fish and corals?

Thanks in advance!

 

[andrewey]

7.8 is perfectly normal for a reef tank. You shouldn't worry about it.


I can't speak to the overall health of the corals or the difference in growth rates I might have gotten had my pH been higher, but I never measured pH on my first SPS tank. Everything grew well and looked great for about four years before I finally hooked up two calibrated pH probes and discovered my pH was sitting between 7.65 and 7.9. -the windows were rarely opened and I had five dogs. I eventually plumbed the skimmer line outside and raised the pH to 8.0-8.2. I noticed a slight uptick in SPS growth, but otherwise nothing changed. Long story short, I doubt you'll notice anything while you run at 7.8 for a bit.

 

[Randy Holmes-Farley]

At a pH below about 7.8, aragonite Coral skeletons and organism shells can begin to slowly dissolve, so I’d try strongly to keep pH At 7.8 or higher. In the pH 7.8 to 8.2 range, lower pH can make hard corals have to work harder to grow skeletons, but they seem to do it ok, maybe mostly because they can do it when the pH is highest during the day.

 

[lilgrounchuck]

My tank was in the basement in my last place and this one and I’ve had swings between 7.8 and 8.1 depending on time of day, number of people over, furnace running, etc and I haven’t noticed anything negative.

 

[NakedReefer]

At a pH below about 7.8, aragonite Coral skeletons and organism shells can begin to slowly dissolve, so I’d try strongly to keep pH At 7.8 or higher. In the pH 7.8 to 8.2 range, lower pH can make hard corals have to work harder to grow skeletons, but they seem to do it ok, maybe mostly because they can do it when the pH is highest during the day.

This would take considerable time, the OP is treating, not keeping levels below your theoretical standard for an extended time.

 

[lilgrounchuck]

Also, fwiw I ran a reFelix treatment a while back and nothing skipped a beat with my skimmer being off.

 

[Randy Holmes-Farley]

This would take considerable time, the OP is treating, not keeping levels below your theoretical standard for an extended time.

Then he shouldn't be concerned. I didn't say he should be.

I was answering the question posed in the title exactly as written.

 

[Randy Holmes-Farley]

My tank was in the basement in my last place and this one and I’ve had swings between 7.8 and 8.1 depending on time of day, number of people over, furnace running, etc and I haven’t noticed anything negative.

Have you ever run it higher to know if there is anything negative?

 

[lilgrounchuck]

Have you ever run it higher to know if there is anything negative?

Yeah, it’s normally at 8.2-8.3.

 

[Ed Chan]

Thanks for all the input! Was originally concerned since I was alerted by my Apex controller when pH dipped below 7.80.

 

[NakedReefer]

Then he shouldn't be concerned. I didn't say he should be.

I was answering the question posed in the title exactly as written.

Then perhaps reading his entire post would behoove you.

 

[Silver14SS]

Asking because I just started my treatment of Flux Rx to address GHA and in doing so, have to turn off my skimmer. Normally I have my CO2 scrubber attached to the skimmer which gets my pH to fall within 8.00 and 8.25.

My first night without the CO2 scrubber running and right now I'm at a low of 7.79

Fish seem fine so far, and I know that generally my tanks pH reaches its low point now (11am PST) and raises or peaks closer to midnight.

Should I be concerned if my pH drops to this level? What would the negative effects be on both fish and corals?

Thanks in advance!

Can you keep your skimmer running without the cup to still aerate the water? I did that when I used Flux Rx, removed the cup and put a piece of acrylic over the skimmer neck to keep it from spraying everywhere.

 

[Ed Chan]

That could definitely be an option.

By chance, when did you turn your skimmer back on after treating your tank with Flux Rx? After the recommended 72 hours or at the end of the 2 week treatment cycle?

Can you keep your skimmer running without the cup to still aerate the water? I did that when I used Flux Rx, removed the cup and put a piece of acrylic over the skimmer neck to keep it from spraying everywhere.

 

[Randy Holmes-Farley]

Yeah, it’s normally at 8.2-8.3.

OK, I thought you said

"My tank was in the basement in my last place and this one and I’ve had swings between 7.8 and 8.1 depending on time of day, number of people over, furnace running, etc and I haven’t noticed anything negative. "

which didn't imply it was ever anywhere else, nor that it was being compared tot eh same tank at higher pH.

It is a common problem on this forum that folks answer a question by saying what they do and it must be OK, without saying anything about how it might be different. Applies to water changes, temperatures, and all sorts of chemical questions.

 

[Silver14SS]

By chance, when did you turn your skimmer back on after treating your tank with Flux Rx? After the recommended 72 hours or at the end of the 2 week treatment cycle?

It's been a while so I don't remember exactly, sorry . I think I followed the directions and the skimmer was still overflowing, so I ran it without a cup at a slow skimmer pump speed until the skimmer calmed down.

 

[NakedReefer]

Can you keep your skimmer running without the cup to still aerate the water? I did that when I used Flux Rx, removed the cup and put a piece of acrylic over the skimmer neck to keep it from spraying everywhere.

If you do not want to cover it you can also just let the skimmer overflow and you'll be fine

 

[Silver14SS]

If you do not want to cover it you can also just let the skimmer overflow and you'll be fine

The bubbles popping getting water all over the sump bracing motivated me to cover it.

 

[Randy Holmes-Farley]

Then perhaps reading his entire post would behoove you.

I did, thank you very much. This is my forum and I try to read every post and answer the questions there. I answered the more general question since many folks like yourself answered without providing the scientific insight that I thought the OP and others might benefit from.

 

[lilgrounchuck]

OK, I thought you said

"My tank was in the basement in my last place and this one and I’ve had swings between 7.8 and 8.1 depending on time of day, number of people over, furnace running, etc and I haven’t noticed anything negative. "

which didn't imply it was ever anywhere else, nor that it was being compared tot eh same tank at higher pH.

It is a common problem on this forum that folks answer a question by saying what they do and it must be OK, without saying anything about how it might be different. Applies to water changes, temperatures, and all sorts of chemical questions.

I guess I could have elaborated a bit more. Normal is 8.2-8.3 and my swings have been on the down side between 7.8-8.1 depending on the aforementioned environmental changes.

 

[NakedReefer]

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