What causes alk fluctuations through the day and how do I stabilize?

[livinlifeinBKK]

Hey guys, I posted a similar thread last week but my question's focus was a little different. Now I'm trying to figure out what causes my alk to fluctuate during different times of the day so I can stabilize it as much as possible so I can feel more confident about adding some of the more challenging SPS corals. I've been keeping a journal of my alk readings taken at different times of the day for the past 5 days and use an AF test kit for the readings. The records indicate that my alk fluctuates by about .5-.6 dkh during a 24 hour period. It ranges from between about 8.2-8.8 during 24 hours. I think after another week of testing multiple times a day I'll be able to give even more precise info on how the time of day affects it but from these 5 days it seems to rise steadily during the morning and peak around noon, then slowly decline after peaking. Again, these readings weren't taken with a Hanna tester so they may be slightly off but there's definitely a trend. What do you guys think causes this and how can I increase stability? Btw, tank is a nano about 6 months old.

 

[Dennis Cartier]

The decline in alkalinity will normally coincide with your photo period as corals uptake alkalinity. How are you dosing the tank?

Typically dosing during the photo period, spread throughout the period, is the easiest way of minimizing the alkalinity swing.

 

[livinlifeinBKK]

The decline in alkalinity will normally coincide with your photo period as corals uptake alkalinity. How are you dosing the tank?

Typically dosing during the photo period, spread throughout the period, is the easiest way of minimizing the alkalinity swing.

Since it's a nano and I don't have many corals yet I haven't begun dosing, just weekly water changes right now

 

[Dennis Cartier]

Hmm, if you are not dosing, then you should not see any swings, only declines. You are seeing a daily swing in alkalinity? Then you need to examine your test method, as without dosing, or doing a water change, you should not see an increase in alkalinity.

 

[livinlifeinBKK]

Hmm, if you are not dosing, then you should not see any swings, only declines. You are seeing a daily swing in alkalinity? Then you need to examine your test method, as without dosing, or doing a water change, you should not see an increase in alkalinity.

Ok...I'll be extra careful with my testing...I know that the breakdown of nitrates can cause alk changes...I do dose a product that decreases nitrate and phosphate so could that be the culprit? Also maybe I need to test my RODI water I use to top up evaporated water to see if I need to replace the filters

 

[Dennis Cartier]

What product are you dosing?

It is true that as nitrate is used, the alkalinity that was used to make it will be returned, raising alkalinity. That only occurs when your nitrate level is decreasing. Do you have high nitrate in the tank?

 

[livinlifeinBKK]

What product are you dosing?

It is true that as nitrate is used, the alkalinity that was used to make it will be returned, raising alkalinity. That only occurs when your nitrate level is decreasing. Do you have high nitrate in the tank?

No, the nitrate isn't high but I assumed that's because of the product I dose...AF Pro Bio F

 

[livinlifeinBKK]

Maybe I'll experiment with not adding that supplement for a week

 

[Dennis Cartier]

Unless that product contains nitrate directly, then it will not affect alkalinity. However if your nitrate is not high, I don't think you need to dose anything to lower it. So discontinuing is a fine idea.

 

[J1a]

If your nitrate doesn't change dramatically, it is not contributing significantly to the alk change.

 

[livinlifeinBKK]

I'll discontinue use for a week and see if I notice increased stability... the reason I really started using it was due to phosphates that were a little high...also worth noting is that with the AF Kh test just .02 ml of titrant can be the difference between a reading of .3 or .4 dkh so it is possible I need to pay extra attention to my readings, especially since the top line where the plunger needs to be filled to before adding the titrant has worn off due to use

 

[Biff0rz]

It's normal for your alk to change through the day What's really changing it is the PH which is related to the photoperiod. If you want to stabilize alk more, stabilize PH. Unfortunately it's challenging to stabilize PH as many things affect it but it's possible. You can also stabilize alk by dosing but that's just adding more/less vs stabilizing it.

 

[livinlifeinBKK]

You guys sound pretty knowledgeable about this so do you think I should be ok adding a less expensive acro since it sounds like the fluctuating readings I'm getting are most likely due to testing error (or a slightly changing pH which I just saw commented)

 

[CookieRdReef]

Evaporation will also change alk. If you have an ato then nevermind.

 

[livinlifeinBKK]

Evaporation will also change alk. If you have an ato then nevermind.

Yeah I've got an ato

 

[livinlifeinBKK]

It's normal for your alk to change through the day What's really changing it is the PH which is related to the photoperiod. If you want to stabilize alk more, stabilize PH. Unfortunately it's challenging to stabilize PH as many things affect it but it's possible. You can also stabilize alk by dosing but that's just adding more/less vs stabilizing it.

So in your opinion it's probably best to just leave it be and focus on my testing? Like I said, with the test kit I use just one extra drop of titrant (~.02 ml) changes the reading by .3 or .4 dkh

 

[Nano sapiens]

Typically, reef keepers with stonies check alk at the same time of day and strive to keep that number as consistent as possible day to day.

A rise in pH and alk during the lighting period is inevitable when photosynthetic organisms (like coral) uptake calcium carbonate. One could use a refugium with macro algae (like Chaeto) and maybe calcareous alga like Halimeda on a reverse lighting schedule to help balance out the pH and alk swings (assuming you aren't intending to vary the amount of alk being dosed over a 24 hr period).

Whether there would be any noticeable benefit derived from smoothing out a 0.3 - 0.5 dKh daily alk swing, I'll leave that to those that are successful with uber-finicky Acros.

 

[livinlifeinBKK]

Typically, reef keepers with stonies check alk at the same time of day and strive to keep that number as consistent as possible day to day.

A rise in pH and alk during the lighting period is inevitable when photosynthetic organisms (like coral) uptake calcium carbonate. One could use a refugium with macro algae (like Chaeto) and maybe calcareous alga like Halimeda on a reverse lighting schedule to help balance out the pH and alk swings (assuming you aren't intending to vary the amount of alk being dosed over a 24 hr period).

Whether there would be any noticeable benefit derived from smoothing out a 0.3 - 0.5 dKh daily alk swing, I'll leave that to those that are successful with uber-finicky Acros.

At this point since it's a nano with only a few corals and a clam using the alk I'd just prefer not to get a doser yet because from what I gathered from most commenters my testing is most likely to be a tiny bit off since I don't have high nitrates being depleted and I'm not just seeing a steady decline but a slight increase and decrease over a 24 hour period...I'm not looking to throw some super fragile designer acros in at this point since the tank is still young and I still have plenty to learn, I was just hoping to achieve enough stability to sustain a couple maybe $30 acros...do you think they'd do ok judging by what you know from this thread?

 

[Nano sapiens]

At this point since it's a nano with only a few corals and a clam using the alk I'd just prefer not to get a doser yet because from what I gathered from most commenters my testing is most likely to be a tiny bit off since I don't have high nitrates being depleted and I'm not just seeing a steady decline but a slight increase and decrease over a 24 hour period...I'm not looking to throw some super fragile designer acros in at this point since the tank is still young and I still have plenty to learn, I was just hoping to achieve enough stability to sustain a couple maybe $30 acros...do you think they'd do ok judging by what you know from this thread?

I can say from experience with my current 12 g that I was able to successfully keep and grow a few hardy Acros before they outgrew and/or became too aggressive for this small mixed reef.

However, I didn't try an Acro until a few years had passed. Assuming consistently stable conditions (especially alk), you may be able to keep a hardy Acro at 6 months (each system matures differently).

 

[livinlifeinBKK]

I can say from experience with my current 12 g that I was able to successfully keep and grow a few hardy Acros before they outgrew and/or became too aggressive for this small mixed reef.

However, I didn't try an Acro until a few years had passed...

Why did you decide to wait a few years?