Low nightly PH, should I add kalk

[Wtyson254]

My system has ~ 200L total water volume. I run a Red Sea 300 Skimmer with a recirculating CO2 scrubber (air Intake from the skimmer cup). I live in an NYC apartment and likely have elevated CO2 in the apartment (gas stove etc, 2 people + cat). I currently dose 3ml of Tropic Marin All-4-Reef and 5 ML of Red Sea alk. I dose the extra 5ML of alk as my system seems to consume alk at a much higher rate than Ca. At this point I titrate my All-for-reef dosing based on Ca, then supplement the alk deficit with the Red Sea alk supplement.

My question is if it would be beneficial to switch to/or add kalkwasser.



I ordered an air CO2 meter on amazon so I will have Air CO2 level data.

 

[JoshO]

How is your reef doing in terms of growth?

 

[Wtyson254]

How is your reef doing in terms of growth?

It’s slower than I would like. Coloration is good but growth rates are not wonderful.

My par is 200-350 across most of the tank, and I have an MP40qd and a Gyre 330 (both running @ 50%)

 

[JoshO]

It’s slower than I would like. Coloration is good but growth rates are not wonderful.

My par is 200-350 across most of the tank, and I have an MP40qd and a Gyre 330 (both running @ 50%)

Does the flow reduce overnight?

 

[Wtyson254]

Does the flow reduce overnight?

Not appreciably I run the MP40 on nutrient transport mode 24/7 and the gyre runs at 60% during the day and 40% at night

 

[Wtyson254]

The return is doing 400gph for roughly 8x turnover

I do run biopellets in a reactor in the sump.

 

[JoshO]

Not appreciably I run the MP40 on nutrient transport mode 24/7 and the gyre runs at 60% during the day and 40% at night

Might be worth running the gyre at 60% at night and see if has any benefit, your alk is at a good level now

 

[Wtyson254]

This ph graph is for the last 24 hours, the lights turn on at 10:30 (when the downslope of the graph leveled out), and I opened the windows in my apartment at 2pm (when you see the sudden rise in ph)

 

[JoshO]

Your alk is at a pretty good level now which makes me think you don't need to change that. Definitely seems like an oxygenation issue from the numbers, especially if it started to rise once the windows are open. Is there any chance you could leave a window open overnight to test this theory?

 

[Wtyson254]

Your alk is at a pretty good level now which makes me think you don't need to change that. Definitely seems like an oxygenation issue from the numbers, especially if it started to rise once the windows are open. Is there any chance you could leave a window open overnight to test this theory?

Yea, weather willing, I will do it tonight. Though this will not be an option in the summer months.

My reasoning for using Kalk instead of/in addition to my current Alk dosing is that I would essentialy be dosing free hydroxide into the tank which would scavenge some H+.

 

[JoshO]

Yea, weather willing, I will do it tonight. Though this will not be an option in the summer months.

If it helps stabilise then I'm sure there will be a way we can find for summer!

 

[Randy Holmes-Farley]

A high or very high pH additive might help the lower pH. It's a tough situation that you describe.

 

[Wtyson254]

@Randy Holmes-Farley Is there a specific additive you would recommend?

 

[Wtyson254]

So I’m currently adding the following to my 200L total water volume tank per day.

5ML of Red Sea alk (0.25 dKH/l) and 3ml of all for reef (0.084 dKH/l) and (0.6mg/l Ca)

So total Alk added across all sources is 0.334 dKH/l

Total Ca is 0.6 mg/l or 0.6 ppm

Does this math look correct?

 

[Wtyson254]

The Brightwell Kalk +2 Instructions state
That 1ml saturated solution will increase Ca in 3.785L by 2.3ppm, so with a total system volume of 200L, 32.1ml saturated solution will increase Ca by 2.3 ppm. So 13.95ml will increase Ca by 1 ppm.

How do I find out how much alk will increase?

 

[Wtyson254]

This is my overnight PH with the window partially open (was super windy and raining so could not open them substantially)

 

[Wtyson254]

I opened them fully this morning

 

[Wtyson254]

Additional calculations:

From my research each ml of saturated Kalk will increase the dKH of 200L by 0.0007 dKH so if I am only dosing 14ml (to meet the need of my Ca consumption) I will only be increasing ALk by 0.01 dKH and will therefore need to make up for the remainder of alk consumption with ALk buffer? Does this sound correct?

I can’t help but wonder if my calcium consumption will increase considerably when when my ph increases 2nd to greater metabolic uptake.