Chronically low pH

LVReefer94

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My pH was doing pretty good at a range of 8.0's - 8.1's sometimes it would hit 8.2 and I was happy with that as corals we're "surviving" and some seemed to be thriving but now my pH has hit lows down to 7.76 but it mainly doesn't go under 7.8. I started running a skimmer and my apex doses 100 ml of full strength kalkwasser ever 6 hours because my daily alk consumption from my Trident tests is very low and the kalk dosing does lower my salinity per the conductivity probe you can watch it go down from 35 ppt to 33.5 while adding that 400 ml of kalkwasser through the day even though the extra freshwater not needed by the auto top off will just evaporate over the day the salinity will not come back up till I manually fix it. The kalk does raise the pH after dosing but not by much, sometimes really none at all almost. Any suggestions? Im stuck right now because I don't want my alk getting crazy high, id love to be dosing more kalk but the alk consumption just isn't there to justify it. What should I do about this?? CO2 scrubbing is not an option, windows open during the day doesn't help at all. I've tried it too many times to count.
 
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CuzzA

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Assuming your salinity is accurate, alk is okay, and with all windows open, if it doesn't go higher than your pH probe could be off. Of course there's also the reality that there is more co2 in the air than ever before during modern times, so there really may not be much you can do. 7.8 pH is not uncommon and is acceptable for a home tank.
 
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LVReefer94

LVReefer94

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Not sure by your statement. Are you using an ATO for evaporation or just adding Kalk for any evaporation?
ato with just plain ro water and a doser pumping in kalk, I feel like my certain situation could be better if I put Kalk in my ato even though most say its not a good option because of pump life and saturation boundaries but as much as my ato runs vs my dosing pump it could do me justice by putting kalk in my ato.
 
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rhostam

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ato with just plain ro water and a doser pumping in kalk, I feel like my certain situation could be better if I put Kalk in my ato even though most say its not a good option because of pump life and saturation boundaries but as much as my ato runs vs my dosing pump it could do me justice by putting kalk in my ato.

I had a similar issue. Your numbers aren’t bad and chasing specific values may not be worth the trouble if you’re with acceptable range and those numbers are stable/ consistent.

Having said that, I stopped ATO + kalkwasser because I have had ATO FAIL OPEN once or twice due to optical sensors malfunctioning (now corrected) and float valve getting stuck (also now corrected). ATO + kalkwasser in those instances would have led to huge spikes in pH and I decided against that risk. Never mind the cleanup of the ATO chamber and my PMUP and optical sensors for RODI fill getting clouded being unable to read correctly when covered in kw residue.

Now I run a setup like yours where ATO operates independently from a kalkwasser reactor. I have the kw reactor fed with a DOS that only runs when the following conditions:
  • for 1 min on, 15 min off (so that Apex has a chance to measure a reading for pH and mitigate potential spikes)
  • if pH < 8.20
  • Alk < 10.50
  • if ATO PMUP is off
  • sump high optical sensor is open
 
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LVReefer94

LVReefer94

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I had a similar issue. Your numbers aren’t bad and chasing specific values may not be worth the trouble if you’re with acceptable range and those numbers are stable/ consistent.

Having said that, I stopped ATO + kalkwasser because I have had ATO FAIL OPEN once or twice due to optical sensors malfunctioning (now corrected) and float valve getting stuck (also now corrected). ATO + kalkwasser in those instances would have led to huge spikes in pH and I decided against that risk. Never mind the cleanup of the ATO chamber and my PMUP and optical sensors for RODI fill getting clouded being unable to read correctly when covered in kw residue.

Now I run a setup like yours where ATO operates independently from a kalkwasser reactor. I have the kw reactor fed with a DOS that only runs when the following conditions:
  • for 1 min on, 15 min off (so that Apex has a chance to measure a reading for pH and mitigate potential spikes)
  • if pH < 8.20
  • Alk < 10.50
  • if ATO PMUP is off
  • sump high optical sensor is open
How many ml dos your dos put through the reactor for that 1 min and how many gallons of water are you dealing with?
 

rhostam

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How many ml dos your dos put through the reactor for that 1 min and how many gallons of water are you dealing with?
About 10-20 ml depending on time of day. I can’t program specific volume (like 5 ml now) so there is the regular scheduled volume of 5 liters a day, but I limit the time that schedule can actually dose by using the OSC command.

Total volume is only 50 gallons for the system in question. It keeps pH relatively stable with swings being 0.1 to 0.09 of a point. So much so that I plan to use the exact same setup with my new WB P7225 build.

I had the same problem as you do. Like many others I don’t chase specific numbers, but I do aim for stability.
 

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