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.
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.
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.
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.