Ph vs Temp vs Alk usage, any relation?

Ferrell · Sep 5, 2021

Some background first: my 75 4 year old softy/LPS tank normally runs with following parameters
Temp 77.8-78.3
Alk 8.6-8.8 with 2 part being dosed for 40 sec per hour on a BRS 1.1 doser (soda ash and calcium chloide)
Ph 7.9-8.4
Salinity 34-35 ppt
calcium 440
Magnesium 1450-1500 HW REEFER been that way since day 1

Recently began having AC issues, house still cool but the room tank was in stayed warmer so fans added to sump operated with apex, then fan added at doorway to draw in cooler air, but temp in tank about 4:00 would get above 78.3 then 78.5 then 79. This won’t on about a week before ac guy determined issue. Now during this time ph range kept going lower and lower ultimately to 7.7-8.05 during a 24 hr cycle. What I didn’t realize was during this decreased ph time alk usage dropped dramatically at which time alk spikes to 10.5. DoseRo’s turned off for almost a week to let it come down naturally. i did loose a milka stylo and a grafted cap during this time that were recent additions with nice growth tips and edges.

I guess my question would be, Is there a relation between elevated temp (not really out of acceptable range) and lower ph which results in less alk usage? Would it have to do with Oxygen saturation being greater at lower temps, not that the temp was ridiculously high. Just trying to understand better what was happening.
I know corals grow less (use less 2 part) in lower ph

Since the occurrence my ph is back to normal ranges and alk dosages are increasing. Gone from 10 secs/ hour last week up to 25 sec/hour this week.

Note: I have apex comparison graphs of temp and ph if anyone interested

((FORDTECH)) · Sep 5, 2021

Ferrell said:
Some background first: my 75 4 year old softy/LPS tank normally runs with following parameters
Temp 77.8-78.3
Alk 8.6-8.8 with 2 part being dosed for 40 sec per hour on a BRS 1.1 doser (soda ash and calcium chloide)
Ph 7.9-8.4
Salinity 34-35 ppt
calcium 440
Magnesium 1450-1500 HW REEFER been that way since day 1

Recently began having AC issues, house still cool but the room tank was in stayed warmer so fans added to sump operated with apex, then fan added at doorway to draw in cooler air, but temp in tank about 4:00 would get above 78.3 then 78.5 then 79. This won’t on about a week before ac guy determined issue. Now during this time ph range kept going lower and lower ultimately to 7.7-8.05 during a 24 hr cycle. What I didn’t realize was during this decreased ph time alk usage dropped dramatically at which time alk spikes to 10.5. DoseRo’s turned off for almost a week to let it come down naturally. i did loose a milka stylo and a grafted cap during this time that were recent additions with nice growth tips and edges.

I guess my question would be, Is there a relation between elevated temp (not really out of acceptable range) and lower ph which results in less alk usage? Would it have to do with Oxygen saturation being greater at lower temps, not that the temp was ridiculously high. Just trying to understand better what was happening.
I know corals grow less (use less 2 part) in lower ph

Since the occurrence my ph is back to normal ranges and alk dosages are increasing. Gone from 10 secs/ hour last week up to 25 sec/hour this week.

Note: I have apex comparison graphs of temp and ph if anyone interested

I believe temp has nothing to do with ph changing it’s the co2 in the house effecting the ph. Now the question is does temp change or effect co2 which in turn would effect ph. But let’s see what others say

((FORDTECH)) · Sep 5, 2021

The fans could some how be changing the co2 in the rooms

Ferrell · Sep 5, 2021

Not sure the fans would’ve done it as this room is generally warmer because of the lights and we run fans almost always.

As an aside, I have nowrouted my airflow to the skimmer outside. Ph was awesome all summer up until the ac started acting up so I didn’t do it until now.

Randy Holmes-Farley · Sep 8, 2021

Lower pH generally results in lower alkalinity and calcium consumption, though your much more likely to notice the alk change.

pH changes typically come from lighting changes, aeration changes, or from CO2 in the air changes.

Ferrell · Sep 9, 2021

@Randy Holmes-Farley , I have seen the trend in my tank where higher ph affects/causes alk/cal usage And typically run 8.1-8.4 cycles night to day.

So would the higher temps have affected the O2 or CO2? As temps increase is CO2 absorbed more readily?

Randy Holmes-Farley · Sep 10, 2021

Ferrell said:
@Randy Holmes-Farley , I have seen the trend in my tank where higher ph affects/causes alk/cal usage And typically run 8.1-8.4 cycles night to day.

So would the higher temps have affected the O2 or CO2? As temps increase is CO2 absorbed more readily?

Temperature effects on reef tanks are minor as the range we usually encounter is small. But there is less O2 in seawater at higher temps. CO2 and pH are much more complicated since temperature impacts many different processes that could alter aquarium pH. Simple analysis would suggest that higher temps give higher pH (higher temps generally drive gases out of water), but there are many complicating factors and I would not be sure what predominates.