Alkalinity swings throughout the day

[Miami Reef]

My photoperiod is 4 hours on a dim schedule, then 8 hours with full lights. There’s no ramping (I’m using all T5). 12 hours total of light.

I use a BRS 1.1mL dosing pump to spread my alkalinity throughout those 12 hours.

I tested my tank for 2 days in a row and the results are the same: 9.2dKH a few hours before lights are on. Before lights are off it’s 9.8dKH.

How can I get my alkalinity to be as stable as possible? Should I spread my dose over 24 hours?

 

[Koh23]

Probably i didnt understood correctly, but if at the end of the day you end up with higher value than u started, your dosing is wrong. U add too much solution....

You didnt say your target kh, so, that is important.piece of information that is missing

 

[Miami Reef]

Probably i didnt understood correctly, but if at the end of the day you end up with higher value than u started, your dosing is wrong. U add too much solution....

You didnt say your target kh, so, that is important.piece of information that is missing

I add 200mL (260 gallon tank) which is evenly spread out through 12 hours.

My target Alkalinity is 10dKH.

 

[Garf]

My photoperiod is 4 hours on a dim schedule, then 8 hours with full lights. There’s no ramping (I’m using all T5). 12 hours total of light.

I use a BRS 1.1mL dosing pump to spread my alkalinity throughout those 12 hours.

I tested my tank for 2 days in a row and the results are the same: 9.2dKH a few hours before lights are on. Before lights are off it’s 9.8dKH.

How can I get my alkalinity to be as stable as possible? Should I spread my dose over 24 hours?

The general wisdom seems to be that photosynthesis drives Alk consumption in coral. So, yours is dropping at night? Have you got a lit Refugium on a reverse lighting schedule? Don’t suppose you’ve got high pH at night?

 

[Miami Reef]

The general wisdom seems to be that photosynthesis drives Alk consumption in coral. So, yours is dropping at night? Have you got a lit Refugium on a reverse lighting schedule? Don’t suppose you’ve got high pH at night?

I actually have very high pH at night.

I don‘t use refugium/reverse lighting. I just dose sodium hydroxide for alkalinity. My pH maxes at 8.55 and…just look at this graph.

My lights (and dosing) stops at 11pm. pH maxes 8.55

My pH comes down to 8.4 by 4:30am.

 

[Miami Reef]

@Randy Holmes-Farley

Maybe this data would be of interest to you?

 

[Miami Reef]

So I started dosing 210mL every hour around the clock

I tested my alkalinity at 7am (4 hours prior to lights) and 9pm (2 hours before lights off) and they both tested at 9.2dKH.

Now night time will be dosed as well. Let’s see if alkalinity rises or drops by tomorrow morning.

My pH is currently 8.36. I will see how the pH trends with hydroxide overnight and see if there’s any alkalinity consumption. If it rises above 9.2, then photosynthesis contributes to alkalinity consumption, if alkalinity is maintained or drops, despite dosing an high pH additive for alkalinity, then pH has an impact on alkalinity consumption with lights off.

 

[Miami Reef]

I tested my alkalinity (it’s about 10am).

I dosed alkalinity overnight and it only rose .3dKH. (from 9.2-9.5)

Seems like there is some consumption at night, if not, I’d expect it to rise much more.

pH and alkalinity definitely seems more stable with 24 hour dosing. I think I’ll keep it like this and see how it goes. :)

 

[Miami Reef]

Between day and night, pH had a .1 difference which is much more stable than the .29 difference I had the day before.

 

[14 foot reef]

I do the opposite, I DOS Kalk reverse the main display lighting schedule. My Alk has never been more stable than with this reverse lighting method.

 

[thatmanMIKEson]

Alkalinity dosing 24/7 has helped me, im currently 140ml of sodium carbonate a day in my 120, I shoot for 7-8dkh right now

 

[Miami Reef]

Alkalinity dosing 24/7 has helped me, im currently 140ml of sodium carbonate a day in my 120, I shoot for 7-8dkh right now

I think this way will work for me. Kind of like how a calcium reactor works. :)

 

[RIC13]

I dose kalk via the ATO and supplement it by dosing alk. In the beginning, when I dosed alk around the clock, I noticed that my dkh wasn’t stable. It was always higher during the photoperiod. Today, I still run kalk in my ATO, but I switched to dosing the alk multiple times in small doses overnight and have seen the dkh stabilize. I’m very happy with the health of my SPS.

 

[Randy Holmes-Farley Verified Community Expert]

I dose kalk via the ATO and supplement it by dosing alk. In the beginning, when I dosed alk around the clock, I noticed that my dkh wasn’t stable. It was always higher during the photoperiod. Today, I still run kalk in my ATO, but I switched to dosing the alk multiple times in small doses overnight and have seen the dkh stabilize. I’m very happy with the health of my SPS.

Could that be due to higher evaporation during the day rather than lesser demand? Demand is typically higher (in some cases almost completely) during the day so I'm wondering if you are inverting that by dosing more during the day as well.

How much does your pH vary day to night? pH is a substantial driver of demand.

 

[RIC13]

Could that be due to higher evaporation during the day rather than lesser demand? Demand is typically higher (in some cases almost completely) during the day so I'm wondering if you are inverting that by dosing more during the day as well.

How much does your pH vary day to night? pH is a substantial driver of demand.

I cannot speak confidently about the rate of evaporation overnight vs. during the day. I did, however (because of your question), test the PH for the first time overnight after the lights had been off for several hours and found the PH was 7.8-8.0. My practice is to test during the day and have found it to be 8.2-8.4 which I attribute to the benefits of kalk.