Gigajoulz

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Average Parameters & Equipment
Temp.......76.5-77.5F
Salinity.......1.0255 SG
NO3-API.......10-20 ppm range
PO4-Hanna.......0.17 ppm

pH.......7.50-7.68 observed range
Alk-Hanna.......10.6 dKH
KH-Salifert.......10.4 dKH
Calcium-API.......out-of-range / 580-600ppm (29-30 drops of API reagent 2)
Mg-Salifert.......1450 ppm
(see attached excel file for complete readings)

Standard 75-gal tank
Apprx 2 5-gal buckets of rocks, 2 bags of crushed coral, and a bag of live sand
Fluval 407 canister filter
20-gal sponge filter
RODI/saturated Kalkwasser top off 750 ml/day
Feeding one cube of PetSmart frozen brine shrimp per day

Weekly to bi-weekly water changes (mostly every Saturday, I do a 15-20% water change using Coral Pro reef salt, the black bucket. My RODI adapter on the sink broke recently so I haven't done a water change in almost 10 days at the time of my readings above)



Hello everyone,

I am posting today to address an issue I am facing with chronically low pH in my 75-gallon saltwater tank, despite high readings and dosing saturated Kalkwasser (2 tbsp per gallon). Increasing air exchange in the home and on the surface of the water is not feasible, so I am looking for alternative solutions.

To provide context for my chemistry question, my tank has been running since August 1st, 2022, with about 2x 5-gallon buckets of medium and small-sized rocks, two large bags of crushed coral bed, and a small bag of live sand. We have a Kalk doser/top off and a 20-gallon sponge filter running. The bubbler appeared to raise the pH by 0.05 points, but it is hardly noticeable when the pH is as low as 7.5 sometimes. We have green coralline growing all over the rocks and spotting on the glass, but our Zoas, Xenia, and other soft corals have not been growing very well, and some coral frags have died. Some stoney frags have turned a light color and seem to be melting or receding.

The bio load on the tank includes two naked clownfish, two fire fish, a bi-color blenny, a pigmy angel fish, a six-line wrasse, three blue chromis, and a small blue hippo tang (11 fish). We have a variety of snails (about 5-10 alive), some small red-legged crabs (which have been killing some of the snails for their shells) and just added a peppermint shrimp for aptasia. We have some aphasia and vermatid snails, but no ich or other diseases that I have noticed.

The tank has always had a pH average of 7.5-7.6, rarely above 7.8 pH except when dosing soda ash, which temporarily raises the pH to around 8.0. However, the alkalinity raises too high and the pH goes back down to 7.5 by the next morning.

I believe that something is over buffering the water, preventing the pH from rising, or something is actively acidifying the water. I am confused about whether alkalinity and calcium, which are relatively high, especially if I am dosing calcium hydroxide, should be shifting the tank’s alkalinity from bicarb to carbonate, raising pH, or if the Kalk should be lowering the water’s buffering capacity. When I add soda ash to the tank, this temporarily raises pH by around 0.5 points, but severely raises alk over time if dosed regularly, and the pH does not stay elevated for very long at all.

Lately, I have been dosing Kalkwasser in an RODI top off 5-gal bucket, where my doser runs 750ml/24 hrs, doing around 31ml once every hour. This has raised the alkalinity to 10.5 dKH, while the calcium has slightly raised by 20ppm. Before I set up the doser/top off, my calcium was already 580ppm, but my alk was roughly 8.0-8.5 dKH, so Kalkwasser has only raised my Alk but not the Calcium. My first bucket of Kalk was mixed at 1/2 tbsp per gal with 60ml of vinager, which actually proved to lower my nitrates and phosphates, however, I was in Zone 4 of RHF's ALK/CAL ratio. Since that bucket ran out, I've upped the dose to 2 tbsp per gallon but didn't add vinager this time. I'm closer to Zone 1 (not quite there between 10.6 dKH and 580 Cal), but the pH is still in the toilet.
1681653801652.png


I am considering stopping dosing Kalkwasser and instead dosing a soda ash supplement in smaller doses to see how this affects the Alk and pH over time. Alternatively, I am considering dosing Magnesium Hydroxide with Kalkwasser to increase the solubility of bi-carb and carb so that the additional hydroxide better reacts with bi-carbonate and the donated hydrogen from carbonic acid. The only other thing I can I think of is what is going into the tank, which is one cube of food per day. I tested the pH in a 100mL of water after it melted and the pH was 7.2, so I do not think its directly caused by adding food. Another cause might be an over active bio load/high nitrification, which does lower pH, but my fish load is only 11 fish for 75 gallons, and we recently just took out 6 clownfish because they started to pair off and fight, so the bio load has gone down in the last two weeks. At this point I am lost in the chemistry.

I have attached my Microsoft Excel Tank Maintenance file (with blank tabs if anyone would like to use the file themselves) if anyone needs a closer look at my readings over a longer period of time. My readings go back to the start of this tank, in August 2022.

Any advice or insight is greatly appreciated. Thank you.
 

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Gigajoulz

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Also, before we go blaming the calibration on the pH meter, I calibrated it recently and keep the diode end submerged in the tank when its not in use (its just one of those cheap, $35 red Hanna pH tested). Every few days, I take it out of the tank and put it in the HCl cleaning solution for half an hour, rinse, and put it back in the tank. I'm looking into the Milwaukee pH meter for constant readings, but in the mean time, I use my pH meter submerged in the top of the tank near the surface of the water, near the heater. It has not been stored dry.

That being said, until I get the Milwaukee, I intend to at least get some pH strips or another cheap meter to get an average pH.

Any advice would be appreciated. I have been reefing for about a year, and this has been my most successful tank.

How do you maintain pH in your tank?
 
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Average Parameters & Equipment
Temp.......76.5-77.5F
Salinity.......1.0255 SG
NO3-API.......10-20 ppm range
PO4-Hanna.......0.17 ppm

pH.......7.50-7.68 observed range
Alk-Hanna.......10.6 dKH
KH-Salifert.......10.4 dKH
Calcium-API.......out-of-range / 580-600ppm (29-30 drops of API reagent 2)
Mg-Salifert.......1450 ppm
(see attached excel file for complete readings)

Standard 75-gal tank
Apprx 2 5-gal buckets of rocks, 2 bags of crushed coral, and a bag of live sand
Fluval 407 canister filter
20-gal sponge filter
RODI/saturated Kalkwasser top off 750 ml/day
Feeding one cube of PetSmart frozen brine shrimp per day

Weekly to bi-weekly water changes (mostly every Saturday, I do a 15-20% water change using Coral Pro reef salt, the black bucket. My RODI adapter on the sink broke recently so I haven't done a water change in almost 10 days at the time of my readings above)



Hello everyone,

I am posting today to address an issue I am facing with chronically low pH in my 75-gallon saltwater tank, despite high readings and dosing saturated Kalkwasser (2 tbsp per gallon). Increasing air exchange in the home and on the surface of the water is not feasible, so I am looking for alternative solutions.

To provide context for my chemistry question, my tank has been running since August 1st, 2022, with about 2x 5-gallon buckets of medium and small-sized rocks, two large bags of crushed coral bed, and a small bag of live sand. We have a Kalk doser/top off and a 20-gallon sponge filter running. The bubbler appeared to raise the pH by 0.05 points, but it is hardly noticeable when the pH is as low as 7.5 sometimes. We have green coralline growing all over the rocks and spotting on the glass, but our Zoas, Xenia, and other soft corals have not been growing very well, and some coral frags have died. Some stoney frags have turned a light color and seem to be melting or receding.

The bio load on the tank includes two naked clownfish, two fire fish, a bi-color blenny, a pigmy angel fish, a six-line wrasse, three blue chromis, and a small blue hippo tang (11 fish). We have a variety of snails (about 5-10 alive), some small red-legged crabs (which have been killing some of the snails for their shells) and just added a peppermint shrimp for aptasia. We have some aphasia and vermatid snails, but no ich or other diseases that I have noticed.

The tank has always had a pH average of 7.5-7.6, rarely above 7.8 pH except when dosing soda ash, which temporarily raises the pH to around 8.0. However, the alkalinity raises too high and the pH goes back down to 7.5 by the next morning.

I believe that something is over buffering the water, preventing the pH from rising, or something is actively acidifying the water. I am confused about whether alkalinity and calcium, which are relatively high, especially if I am dosing calcium hydroxide, should be shifting the tank’s alkalinity from bicarb to carbonate, raising pH, or if the Kalk should be lowering the water’s buffering capacity. When I add soda ash to the tank, this temporarily raises pH by around 0.5 points, but severely raises alk over time if dosed regularly, and the pH does not stay elevated for very long at all.

Lately, I have been dosing Kalkwasser in an RODI top off 5-gal bucket, where my doser runs 750ml/24 hrs, doing around 31ml once every hour. This has raised the alkalinity to 10.5 dKH, while the calcium has slightly raised by 20ppm. Before I set up the doser/top off, my calcium was already 580ppm, but my alk was roughly 8.0-8.5 dKH, so Kalkwasser has only raised my Alk but not the Calcium. My first bucket of Kalk was mixed at 1/2 tbsp per gal with 60ml of vinager, which actually proved to lower my nitrates and phosphates, however, I was in Zone 4 of RHF's ALK/CAL ratio. Since that bucket ran out, I've upped the dose to 2 tbsp per gallon but didn't add vinager this time. I'm closer to Zone 1 (not quite there between 10.6 dKH and 580 Cal), but the pH is still in the toilet.
1681653801652.png


I am considering stopping dosing Kalkwasser and instead dosing a soda ash supplement in smaller doses to see how this affects the Alk and pH over time. Alternatively, I am considering dosing Magnesium Hydroxide with Kalkwasser to increase the solubility of bi-carb and carb so that the additional hydroxide better reacts with bi-carbonate and the donated hydrogen from carbonic acid. The only other thing I can I think of is what is going into the tank, which is one cube of food per day. I tested the pH in a 100mL of water after it melted and the pH was 7.2, so I do not think its directly caused by adding food. Another cause might be an over active bio load/high nitrification, which does lower pH, but my fish load is only 11 fish for 75 gallons, and we recently just took out 6 clownfish because they started to pair off and fight, so the bio load has gone down in the last two weeks. At this point I am lost in the chemistry.

I have attached my Microsoft Excel Tank Maintenance file (with blank tabs if anyone would like to use the file themselves) if anyone needs a closer look at my readings over a longer period of time. My readings go back to the start of this tank, in August 2022.

Any advice or insight is greatly appreciated. Thank you.
Exact… same… issue. I mean, on the money. Following…
 
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Gigajoulz

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Exact… same… issue. I mean, on the money. Following…
I will say that among all my corals, and since I did that one bucket with vinegar, I have noticed my duncan, green star polyps, pipe organ, sympodium, and some of the zoas have colored up, and I've noticed a significant drop in nutrient levels (NO3 and PO4) . But, fearing that the vinegar was interfering with the OH- in the Kalkwasser, the next bucket (the one running right now) has more Kalk and no vinegar. My Nitrates and Phosphates were reading 5ppm and 0.03-0.05ppm while running 60ml vinegar in 4 gal RODI with 1/2 tbsp Kalk per galk, but since I've up the Kalk to the 2 tsbp without vinegar, I've seen my Nitrates and Phosphates go back up to 10-20ppm and 0.15-0.17ppm,

Vinegar carbon dosing ABSOLUTELY WORKS to reduce nutrients. WORKS 1000x over anything else I've tried to reduce nitrates AND feed my corals. Reef Roids causes hair algae blooms, and performing water changes to reduce nutrients is expensive (RODI resin and salt, plus the time and labor it takes to change the water, PLUS the risk you flood your house like that one time I did when I forgot I was draining water...)

That being said, I'm not enough of a chemist to know how the acidic vinegar is reacting with the hydroxide, and therefore, the pH of the Kalk and its alkalinity potential. My next experiment might be with Ozone / O3.
 

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I will say that among all my corals, and since I did that one bucket with vinegar, I have noticed my duncan, green star polyps, pipe organ, sympodium, and some of the zoas have colored up, and I've noticed a significant drop in nutrient levels (NO3 and PO4) . But, fearing that the vinegar was interfering with the OH- in the Kalkwasser, the next bucket (the one running right now) has more Kalk and no vinegar. My Nitrates and Phosphates were reading 5ppm and 0.03-0.05ppm while running 60ml vinegar in 4 gal RODI with 1/2 tbsp Kalk per galk, but since I've up the Kalk to the 2 tsbp without vinegar, I've seen my Nitrates and Phosphates go back up to 10-20ppm and 0.15-0.17ppm,

Vinegar carbon dosing ABSOLUTELY WORKS to reduce nutrients. WORKS 1000x over anything else I've tried to reduce nitrates AND feed my corals. Reef Roids causes hair algae blooms, and performing water changes to reduce nutrients is expensive (RODI resin and salt, plus the time and labor it takes to change the water, PLUS the risk you flood your house like that one time I did when I forgot I was draining water...)

That being said, I'm not enough of a chemist to know how the acidic vinegar is reacting with the hydroxide, and therefore, the pH of the Kalk and its alkalinity potential. My next experiment might be with Ozone / O3.

All types of organic carbon dosing tend to reduce pH, including vinegar.

Also, did you try the aeration test?


The Aeration Test

Some of the possible causes of low pH listed above require an effort to diagnose. Problems 3 and 4 are quite common, and here is a way to distinguish them. Remove a cup of tank water and measure its pH. Then aerate it for an hour with an airstone using outside air. Its pH should rise if it is unusually low for the measured alkalinity (Figure 2). Then repeat the same experiment on a new cup of water using inside air. If its pH also rises, then the aquarium’s pH will rise simply with more aeration because it is only the aquarium that contains excess carbon dioxide. If the pH does not rise in the cup (or rises very little) when aerating with indoor air, then that air likely contains excess CO2, and more aeration with that same air will not solve the low pH problem (although aeration with fresher air should). Be careful implementing this test if the outside aeration test results in a large temperature change (more than 5°C or 10°F), because such changes alone impact pH measurements.
 
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Why is this?
What do you mean? Why is it not feasible? I have a 75 gallon downstairs and 20 gallon upstairs in my office. I've left the upstairs window in my office open all day and tested the tanks pH and it barely moves. CO2 very well be my issue, because since this post I have added another bubbler to the tank, but if the levels of CO2 in the house are the issue, then its not the tank with the problem its the environment. I'm also a gamer and have lots of techy stuff that I'm not interested in having stolen, so I cant really leave windows open all the time. The new home we are moving to is also only one level, so no upstairs windows to leave cracked.

None the less, I have not found a good way to setup the cup test where I live, but am moving to a new home in the next few weeks. I intend to place the tank on the other side of the garage wall where I can drill through the wall and run some airline hose to the outside. This will ultimately create better air exchange and I can technically close the lids on my tank, but this might affect my evap. I'm leaning more toward a CO2 reactor on the intake of the air pump, because if I run a tube from outside thru the garage, theres no guarantee someone wont be sitting in the drive way idling their car pumping out CO and CO2..

I want to fix this without additives so the aeration test is next on my list. In the mean time, I have been researching Randy's newest formula with CaCl2 + NaHO + MgCl2 + MgSO4. The only thing concerning me with this is the formation of NaCl and I haven't quite figured out how much my salinity would be affected on the weekly and monthly basis between water changes. How much does this formula affect salinity if I dosed, say, 100mL of each gallon per day? I currently dose 500mL of saturated Kalk and its not touching my pH. The bubbler raised my pH by about 0.1 but thats it, it still fluctuations upwards/downwards of ~0.15 pH each say and night.

How much does it cost to have an air exchanger installed on the HVAC fan?
 
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If pH is 7.6 and does not rise with windows open all day, either the tank aeration is poor, or the reading is inaccurately low
Come to think of it, that was done before I added a new air pump and sponge filter to the tank, so aeration at the time was very poor with the windows open. Without that bubbling, the test was null from the start.

I removed the air pump the tank used (borrowed it for the cup test), took it outside with a 1L jar of tank water. Tank water was reading 7.61 pH at 76F, left it outside for an hour and the pH went up to 7.81pH, and then I left it out there for a bit longer (about 3-4 hours on the porch in the shade on the ground because there isn't a table out there), and checked just now and it was 8.0 pH! The temp actually went down in the jar because its cool outside today. The reader is a little cheap thing from Hannah, but its the best I can find locally as I hate to get this kinda thing from online when my LFS has some options. I do intend to set up a Milwaukee reader soon after we move.

I'm a big enough fish to admit when I am wrong, aeration or CO2 definitely seem to be the issue. I will able to confirm this later when we move. We intend to move ourselves first, prep the space for the new tanks, and so the fish will be left at the old house for about a week or so (no dogs, cat or spouse to produce CO2). This is part of the "unfeasibility" I was referring to in testing for CO2. I watched a BRS video that just suggested one go on vacation for a few days and then see how the pH reacts without anything or anyone else contributing to the CO2 production.

But if CO2 levels are the problem, won't aerating the tank more lead to concentrations of CO2 in the tank? I mean, I don't have any bamboo or plants that might cut down on this (and by how much, I couldn't even begin to predict give there are two people, two dogs a cat, and three fish tanks running total). If I technically can't reduce the CO2 in the environment around the tank, I could close the lid and pipe in air, but that changes my evaporation and dosing chemistry. I could leave the lid open and accept the CO2, but I'd have to switch from Kalk to something stronger.

I think Sodium Hydroxide would do it, but what are you thoughts on a CO2 reactor on an air intake? OR adding some tall bamboos? I currently don't have the dosing equipment for a 2-to-3 part solution, but could easily add a second dosing unit. I'm actually overworking the Sentia doser I have now, using it as an ad hoc top off; it thinks my 4 gallon Kalk bucket is a 6500m container. Kalk really didn't raise my pH but it did raise the Alk about 2.5 dKH, Ca remained relatively the same.
 
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Come to think of it, that was done before I added a new air pump and sponge filter to the tank, so aeration at the time was very poor with the windows open. Without that bubbling, the test was null from the start.

I removed the air pump the tank used (borrowed it for the cup test), took it outside with a 1L jar of tank water. Tank water was reading 7.61 pH at 76F, left it outside for an hour and the pH went up to 7.81pH, and then I left it out there for a bit longer (about 3-4 hours on the porch in the shade on the ground because there isn't a table out there), and checked just now and it was 8.0 pH! The temp actually went down in the jar because its cool outside today. The reader is a little cheap thing from Hannah, but its the best I can find locally as I hate to get this kinda thing from online when my LFS has some options. I do intend to set up a Milwaukee reader soon after we move.

I'm a big enough fish to admit when I am wrong, aeration or CO2 definitely seem to be the issue. I will able to confirm this later when we move. We intend to move ourselves first, prep the space for the new tanks, and so the fish will be left at the old house for about a week or so (no dogs, cat or spouse to produce CO2). This is part of the "unfeasibility" I was referring to in testing for CO2. I watched a BRS video that just suggested one go on vacation for a few days and then see how the pH reacts without anything or anyone else contributing to the CO2 production.

But if CO2 levels are the problem, won't aerating the tank more lead to concentrations of CO2 in the tank? I mean, I don't have any bamboo or plants that might cut down on this (and by how much, I couldn't even begin to predict give there are two people, two dogs a cat, and three fish tanks running total). If I technically can't reduce the CO2 in the environment around the tank, I could close the lid and pipe in air, but that changes my evaporation and dosing chemistry. I could leave the lid open and accept the CO2, but I'd have to switch from Kalk to something stronger.

I think Sodium Hydroxide would do it, but what are you thoughts on a CO2 reactor on an air intake? OR adding some tall bamboos? I currently don't have the dosing equipment for a 2-to-3 part solution, but could easily add a second dosing unit. I'm actually overworking the Sentia doser I have now, using it as an ad hoc top off; it thinks my 4 gallon Kalk bucket is a 6500m container. Kalk really didn't raise my pH but it did raise the Alk about 2.5 dKH, Ca remained relatively the same.

If the CO2 is coming from the indoor air, which si the reason to also do the indoor air aeration test, then more aeration with that air may not help, and you'd need to use outside air, or a different solution, such as a CO2 scrubber on the aeration air.
 

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Come to think of it, that was done before I added a new air pump and sponge filter to the tank, so aeration at the time was very poor with the windows open. Without that bubbling, the test was null from the start.

I removed the air pump the tank used (borrowed it for the cup test), took it outside with a 1L jar of tank water. Tank water was reading 7.61 pH at 76F, left it outside for an hour and the pH went up to 7.81pH, and then I left it out there for a bit longer (about 3-4 hours on the porch in the shade on the ground because there isn't a table out there), and checked just now and it was 8.0 pH! The temp actually went down in the jar because its cool outside today. The reader is a little cheap thing from Hannah, but its the best I can find locally as I hate to get this kinda thing from online when my LFS has some options. I do intend to set up a Milwaukee reader soon after we move.

I'm a big enough fish to admit when I am wrong, aeration or CO2 definitely seem to be the issue. I will able to confirm this later when we move. We intend to move ourselves first, prep the space for the new tanks, and so the fish will be left at the old house for about a week or so (no dogs, cat or spouse to produce CO2). This is part of the "unfeasibility" I was referring to in testing for CO2. I watched a BRS video that just suggested one go on vacation for a few days and then see how the pH reacts without anything or anyone else contributing to the CO2 production.

But if CO2 levels are the problem, won't aerating the tank more lead to concentrations of CO2 in the tank? I mean, I don't have any bamboo or plants that might cut down on this (and by how much, I couldn't even begin to predict give there are two people, two dogs a cat, and three fish tanks running total). If I technically can't reduce the CO2 in the environment around the tank, I could close the lid and pipe in air, but that changes my evaporation and dosing chemistry. I could leave the lid open and accept the CO2, but I'd have to switch from Kalk to something stronger.

I think Sodium Hydroxide would do it, but what are you thoughts on a CO2 reactor on an air intake? OR adding some tall bamboos? I currently don't have the dosing equipment for a 2-to-3 part solution, but could easily add a second dosing unit. I'm actually overworking the Sentia doser I have now, using it as an ad hoc top off; it thinks my 4 gallon Kalk bucket is a 6500m container. Kalk really didn't raise my pH but it did raise the Alk about 2.5 dKH, Ca remained relatively the same.
Plants do help but it's going to be a lot of plants to really make any sizeable Dent into the CO2.

Have you thought about an air exchanger? I see some DIY projects on YouTube that are pretty simple. I think even a small one of those would help considerably, more so than any plants would be able to help.
 
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Plants do help but it's going to be a lot of plants to really make any sizeable Dent into the CO2.

Have you thought about an air exchanger? I see some DIY projects on YouTube that are pretty simple. I think even a small one of those would help considerably, more so than any plants would be able to help.
I'm thinking the air exchanger might be more costly that I want to spend on something that may or may not work. We are moving to a single level, 1900 square foot home in a week or two, and the ratings for a ERV (for the humidity also) would cost about $3,000. We need more important things at the moment like a fence for the dogs, but I intend to try running some airline through the garage.

The tank will be on the other side of a wall in the living room from the garage, and on that influent I can put activated carbon and CO2 reacting media to cut out the CO2. This might actually allow the Kalk to do the rest for the pH. I also want to add another sponge filter to the tank with a stronger air pump, which might aerate the tank more, but I'm not sure how the CO2 will be affected.

I will bring more updates to this thread as I have them. I will check out the air exchanger videos on YouTube as well; it might be something I can actually do myself I've just not looked into DIY yet as I expect that system has to be properly tuned or it might drive up heating and cooling costs.
 
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If the CO2 is coming from the indoor air, which si the reason to also do the indoor air aeration test, then more aeration with that air may not help, and you'd need to use outside air, or a different solution, such as a CO2 scrubber on the aeration air.
I appreciate your advise and help thinking through this. I will attempt the air test again today outside and inside to see if the results are repeatable, and compare indoor and outdoor results. This is the first time I've been able to get accurate numbers from the air test. The last time I tried it I was still green in the hobby and had only some test strips. Using the Hanna pH and a salinity reader for its digital thermometer have helped me get clearer results.
 
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I ran another aeration test this evening. I placed a 1L jar of tank water on top of the tank and left it bubbling for one hour. The pH actually went down about 0.02 pH, which is within range of the sensitivity of my reader, on the indoor test. When I ran the test outside, again, I got an increase of at least 0.10 pH.

I'm going to try and run this test again later this week after I recalibrate the pH reader, and will see if I can get clearer or repeated results. The other day the other side test increased as high at 8.0, and this time I saw it as high as 7.8. I wanna try and to see if I can repeat that test where I got it to 8.0 pH.

I think when we move, we are going to invest in a tank with an overflow and sump, in which I could put a skimmer with a CO2 scrubber media reactor to increase aeration and strip the CO2 from the influent air pump. In the vest least I can try a media reactor before I start dosing a strong base solution.
 
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These are my results from the second test, which may can be used to establish a control for when I run this test a third time but this time I want to setup my air pump outside and run the airline inside to where I ran the indoor test (right on top of the tank in a 1L jar) to see how pumping in outside air does. My wide mouth jar has two holes on top that I added RODI fittings to for another purpose, but I can use it to simulate a tank with a closed lid.

TIME - TANK pH - TEST pH - PARAMETER
11:45 - 7.66 pH - 7.68 pH - outdoors, on the ground outside the front door
12:15 - 7.66 pH - 7.83 pH - outdoors, on the ground outside the front door
13:00 - 7.72 pH - 7.92 pH - outdoors, on the ground outside the front door
(I think the A/C or the fan kicked on, circulating air for the tank, may have ruined the control)

13:05 - 7.73 pH - 7.73 pH - indoors, on top of the tank
14:00 - 7.74 pH - 7.81 pH - indoors, on top of the tank
14:30 - 7.72 pH - 7.84 pH - indoors, on top of the tank
17:00 - 7.77 pH - 7.88 pH - indoors, on top of the tank
(again, the fan turning on and off might be accounted for in the tank's fluctuations during the test.)

During the test, I turned off the Kalk doser (waited for it to dose, then turned it off and waited about 3-4 mins for the tank to circulate). I rinsed my tall, wide mouth 1L Pyrex jar (from Target, highly recommend) three times in the tank and sampled 1L for the test. I have a air pump rated for 20 gallons, way overrated for 1L but severely underrated for 75 gallons.

Now that I'm typing out my results, I realized that I completely forgot to take the temperature readings for the outdoor test, but the other day when I ran the test the temp was lower outside than the tank's temp, and the temp dropped about 4 degrees F during the previous outdoors test. I would think that would at least prevent the pH from dropping if the temp dropped a little during the test.

This outdoor test didn't get as high as 8.0 pH like the other day, but it got close and would read about 0.02-0.03 pH higher if I really swished around the pH meter, and this test was ran on the ground with plenty of wind on the day of the test. If I still run the airline from outside and couple that with CO2 scrubbing media, that should at least eliminate most of the environmental CO2 from the equation to a great degree.
 

Randy Holmes-Farley

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These are my results from the second test, which may can be used to establish a control for when I run this test a third time but this time I want to setup my air pump outside and run the airline inside to where I ran the indoor test (right on top of the tank in a 1L jar) to see how pumping in outside air does. My wide mouth jar has two holes on top that I added RODI fittings to for another purpose, but I can use it to simulate a tank with a closed lid.

TIME - TANK pH - TEST pH - PARAMETER
11:45 - 7.66 pH - 7.68 pH - outdoors, on the ground outside the front door
12:15 - 7.66 pH - 7.83 pH - outdoors, on the ground outside the front door
13:00 - 7.72 pH - 7.92 pH - outdoors, on the ground outside the front door
(I think the A/C or the fan kicked on, circulating air for the tank, may have ruined the control)

13:05 - 7.73 pH - 7.73 pH - indoors, on top of the tank
14:00 - 7.74 pH - 7.81 pH - indoors, on top of the tank
14:30 - 7.72 pH - 7.84 pH - indoors, on top of the tank
17:00 - 7.77 pH - 7.88 pH - indoors, on top of the tank
(again, the fan turning on and off might be accounted for in the tank's fluctuations during the test.)

During the test, I turned off the Kalk doser (waited for it to dose, then turned it off and waited about 3-4 mins for the tank to circulate). I rinsed my tall, wide mouth 1L Pyrex jar (from Target, highly recommend) three times in the tank and sampled 1L for the test. I have a air pump rated for 20 gallons, way overrated for 1L but severely underrated for 75 gallons.

Now that I'm typing out my results, I realized that I completely forgot to take the temperature readings for the outdoor test, but the other day when I ran the test the temp was lower outside than the tank's temp, and the temp dropped about 4 degrees F during the previous outdoors test. I would think that would at least prevent the pH from dropping if the temp dropped a little during the test.

This outdoor test didn't get as high as 8.0 pH like the other day, but it got close and would read about 0.02-0.03 pH higher if I really swished around the pH meter, and this test was ran on the ground with plenty of wind on the day of the test. If I still run the airline from outside and couple that with CO2 scrubbing media, that should at least eliminate most of the environmental CO2 from the equation to a great degree.

The issue with both scrubbing and using outdoor air is competition from the tank top. Closing the top may reduce the entry of CO2 into the water there, and would be better than open, but CO2 may still enter.
 
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