pH swings 7.8 to 8.5

[Hamm Corals]

Hi, my tank pH has swings from 7.8 when the lights are off to 8.5 when lights are on?
Why and what do you think is causing this? My corals look good, growth is good, color is good. Just curious if this swing is too much.
Tank parameters
Salinity 34.5
Temp 78.5
Calcium 420
Magnesium 1250
Alkalinity 8.2
Nitrate 20
Phosphate 0.03
Also run a calcium reactor.

 

[Webslinger]

get a sump and alternate light schedule with main tank. Or leave it alone, not a real issue.

 

[Larry L]

Hi, my tank pH has swings from 7.8 when the lights are off to 8.5 when lights are on?
Why and what do you think is causing this?

When the lights come on, the zooxanthellae in the coral and any other algae in the tank start to photosynthesize, which uses up CO2 which makes your pH go up. Then when the lights go out, normal respiration produces CO2 which makes the pH drop.

 

[Hamm Corals]

I have a large chaeto refugium on at night, I guess what my question would be is the drastic swing from 7.8 to 8.5 too big and would it be beneficial to somehow stabilize the pH?
I've read and seen videos on how large swings of the pH are not a good thing to have

 

[HuduVudu]

I have a large chaeto refugium on at night, I guess what my question would be is the drastic swing from 7.8 to 8.5 too big and would it be beneficial to somehow stabilize the pH?
I've read and seen videos on how large swings of the pH are not a good thing to have

It is common to use calcium hydroxide (kalkwasser) with Calcium reactors. You may want to run kalk at night to help boost the PH troughs.

If long term your corals are doing well, then the expense might not be worth it. Your call.

 

[Randy Holmes-Farley Verified Community Expert]

More aeration will reduce or eliminate that pH swing.

 

[Webslinger]

More aeration will reduce or eliminate that pH swing.

till you turn off the lights

 

[Randy Holmes-Farley Verified Community Expert]

till you turn off the lights

I don't agree. Complete aeration gives no pH change day to night, regardless of photosynthesis or respiration, if alk is stable.

In that scenario, the only thing changeable in terms of pH is the home air CO2 level. pH may drop when you are home and rise when you are not regardless of the time of day.

 

[vessxpress1]

I don't agree. Complete aeration gives no pH change day to night, regardless of photosynthesis or respiration, if alk is stable.

In that scenario, the only thing changeable in terms of pH is the home air CO2 level. pH may drop when you are home and rise when you are not regardless of the time of day.

I just put a pH scrubber on my 20 gallon and recirculate the air on the skimmer. It changed my whole pH situation the first day. Partly because the media canister is huge for this size of tank. Before I could barely get back to 8 pH and now I hit 8.25 to 8.3 during the day and drops to about 8.1 at the lowest before lights turn back on. I had a fresh air line going to skimmer from outside for a month and it wasn't cutting it. pH was getting down to 7.78 during the night. Just too much CO2 absorbed in the water and it wasn't getting out. Tanks in a basement and pH seems to improve when we're not home all day to be honest. It would peak at about 8.0 with the fresh air line feeding skimmer from outside.

 

[HuduVudu]

I just put a pH scrubber on my 20 gallon and recirculate the air on the skimmer.

CO2 scrubber?

 

[vessxpress1]

CO2 scrubber?

Here it is temporarily set up. I’ve since mounted it to the wall. Media is kind of expensive for it but I’m experimenting. I got the 7.5 lb bag of media which should get it through a month or more. I haven’t been adding kalk to my top off water yet either.
Basically the skimmer is sucking air from the bubbles popping in the cup to and through the media in that canister. It removes the CO2 from the air bubbles popping and sends that air back to the pump of the skimmer. This is how to make the media last as long as possible.

 

[vessxpress1]

Can you tell when this was added?

 

[HuduVudu]

Here it is temporarily set up. I’ve since mounted it to the wall. Media is kind of expensive for it but I’m experimenting. I got the 7.5 lb bag of media which should get it through a month or more. I haven’t been adding kalk to my top off water yet either.
Basically the skimmer is sucking air from the bubbles popping in the cup to and through the media in that canister. It removes the CO2 from the air bubbles popping and sends that air back to the pump of the skimmer. This is how to make the media last as long as possible.

Yes, that is a CO2 scrubber. I as just kind of curious because I haven't heard of a PH scrubber. Though I have to admit PH Scrubber™ kinda of a cool name because it more describes what really happens

 

[Hamm Corals]

I figured it out!
I had to temporarily move my tank in front of the sliding glass door of my house, and whenever we open the blinds which was happening daily, the pH spikes. The days when I leave the blinds closed the pH doesn't go up so much.

 

[Randy Holmes-Farley Verified Community Expert]

I figured it out!
I had to temporarily move my tank in front of the sliding glass door of my house, and whenever we open the blinds which was happening daily, the pH spikes. The days when I leave the blinds closed the pH doesn't go up so much.

More aeration will reduce that pH peak, but I do not know if changing it is useful or not.

FWIW, the increased photosynthesis from the blinds being open may be desirable.