Kalk..
- Thread starter aaronlp
- Start date
Gary Majchrzak
Team RC
I'd like to strongly reiterate
I'd like to strongly reiterate
I'd like to strongly reiterate
If your Ca/alk/pH levels are high to begin with, ANY type of supplementation can produce bad results.
Caclium hydroxide(CaOH)disassociates in water .The hydroxide joins up with CO2 to form CO3 carbonate; H+joins the party to make some CO3 into HCO3, bicarbonate. The ratio between carbonate and bi carbonate changes by the micro second depending on the amount of hydrogen protons in the water( ph). Alkalinity as we measure it is a measure of this ratio. Carbonate has twice the alkalinity bicarbonate does, since one sparking spot for H+ is already taken in the HCO3. So when you add hydroxide, it raises the alk and the ph by increasing the CO3 side of the carbonate/ bicarbonate raito and sucking up some H+.
This effect is offset over time as CO2 equilibrates to the water from the air or is produced by biological activitty in the tank . The CO2 forms carbonic acid(H2CO3)
as it is hydrolized which along with free H+ liberated from the water (H2O) by it's interaction with CO2 moves the ratrio back towards HCO3 bicarbonate.
Time and amount are the keys. You can only dose so much hydroxide at one time without spiking ph and carbonate to a point beyond solubility with resulting precipitation.
Sprung and Delbeek recommend 1/4tsp of kalk powder per 50 gallons of aquarium water in a given hour as a maximum. This usually works out to dosing fully saturated kalk( 2 tsps per gallon) as top off for a a1.25 % evaporation rate to a minimun 5 to 6 hour spread fro most systems. A 24 hour spread is optimal. If a system needs less c or has higher evapooration less than fully saturated kalk can be used. Most start with a 1 tsp per gallon mix in top off and work up if needed.
This effect is offset over time as CO2 equilibrates to the water from the air or is produced by biological activitty in the tank . The CO2 forms carbonic acid(H2CO3)
as it is hydrolized which along with free H+ liberated from the water (H2O) by it's interaction with CO2 moves the ratrio back towards HCO3 bicarbonate.
Time and amount are the keys. You can only dose so much hydroxide at one time without spiking ph and carbonate to a point beyond solubility with resulting precipitation.
Sprung and Delbeek recommend 1/4tsp of kalk powder per 50 gallons of aquarium water in a given hour as a maximum. This usually works out to dosing fully saturated kalk( 2 tsps per gallon) as top off for a a1.25 % evaporation rate to a minimun 5 to 6 hour spread fro most systems. A 24 hour spread is optimal. If a system needs less c or has higher evapooration less than fully saturated kalk can be used. Most start with a 1 tsp per gallon mix in top off and work up if needed.
Sorry Dave,
The carbonate cycle and it's realtionship to ph is hard to grasp. I keep trying to find ways to state it more simply it but can't seem to. Let me try this:
You add oxide when dosing kalk . The oxide makes carbonate which is a form of alkalinity.It uses CO2 to do so.
Carbonate is not only used by calcifying organisms but also depleted by CO2 as CO2 makes the water more acidic. As it is used Co2 comes back in from the surrounding air.
The water can only hold so much carbonate ; if too much it precipitates.
Timing the oxide addition to match the CO2 coming in and the consumption by the calcareous organisms in the tank is the trick. So it's how much you dose and how fast you dose it what matters.
It's easier if you remember alkaliity is not a thing but a measure of many things (carbonate,bicarbonate,inorganic phosphate, borate, etc) in terms of their combined ability to neutralize acid.
Corals and other calcifying organisms precipitate carbonate and calcium as calcium carbonate. So, we are mostly concerned with carbonate alkalinity not just for it's buffering of acid but also as an essential major element for stony , shelled or tubed animals in our tank . When reading a mesaure of alkalinity we know how much it can buffer acid but also get a good read on how much carbonate we have since carbonate alkalinity typically makes up about 97% of the total alkalinity measurement.
The carbonate cycle and it's realtionship to ph is hard to grasp. I keep trying to find ways to state it more simply it but can't seem to. Let me try this:
You add oxide when dosing kalk . The oxide makes carbonate which is a form of alkalinity.It uses CO2 to do so.
Carbonate is not only used by calcifying organisms but also depleted by CO2 as CO2 makes the water more acidic. As it is used Co2 comes back in from the surrounding air.
The water can only hold so much carbonate ; if too much it precipitates.
Timing the oxide addition to match the CO2 coming in and the consumption by the calcareous organisms in the tank is the trick. So it's how much you dose and how fast you dose it what matters.
It's easier if you remember alkaliity is not a thing but a measure of many things (carbonate,bicarbonate,inorganic phosphate, borate, etc) in terms of their combined ability to neutralize acid.
Corals and other calcifying organisms precipitate carbonate and calcium as calcium carbonate. So, we are mostly concerned with carbonate alkalinity not just for it's buffering of acid but also as an essential major element for stony , shelled or tubed animals in our tank . When reading a mesaure of alkalinity we know how much it can buffer acid but also get a good read on how much carbonate we have since carbonate alkalinity typically makes up about 97% of the total alkalinity measurement.
Sorry Dave,
The carbonate cycle and it's realtionship to ph is hard to grasp. I keep trying to find ways to state it more simply it but can't seem to. Let me try this:
You add oxide when dosing kalk . The oxide makes carbonate which is a form of alkalinity.It uses CO2 to do so.
Carbonate is not only used by calcifying organisms but also depleted by CO2 as CO2 makes the water more acidic. As it is used Co2 comes back in from the surrounding air.
The water can only hold so much carbonate ; if too much it precipitates.
Timing the oxide addition to match the CO2 coming in and the consumption by the calcareous organisms in the tank is the trick. So it's how much you dose and how fast you dose it what matters.
It's easier if you remember alkaliity is not a thing but a measure of many things (carbonate,bicarbonate,inorganic phosphate, borate, etc) in terms of their combined ability to neutralize acid.
Corals and other calcifying organisms precipitate carbonate and calcium as calcium carbonate. So, we are mostly concerned with carbonate alkalinity not just for it's buffering of acid but also as an essential major element for stony , shelled or tubed animals in our tank . When reading a mesaure of alkalinity we know how much it can buffer acid but also get a good read on how much carbonate we have since carbonate alkalinity typically makes up about 97% of the total alkalinity measurement.
The carbonate cycle and it's realtionship to ph is hard to grasp. I keep trying to find ways to state it more simply it but can't seem to. Let me try this:
You add oxide when dosing kalk . The oxide makes carbonate which is a form of alkalinity.It uses CO2 to do so.
Carbonate is not only used by calcifying organisms but also depleted by CO2 as CO2 makes the water more acidic. As it is used Co2 comes back in from the surrounding air.
The water can only hold so much carbonate ; if too much it precipitates.
Timing the oxide addition to match the CO2 coming in and the consumption by the calcareous organisms in the tank is the trick. So it's how much you dose and how fast you dose it what matters.
It's easier if you remember alkaliity is not a thing but a measure of many things (carbonate,bicarbonate,inorganic phosphate, borate, etc) in terms of their combined ability to neutralize acid.
Corals and other calcifying organisms precipitate carbonate and calcium as calcium carbonate. So, we are mostly concerned with carbonate alkalinity not just for it's buffering of acid but also as an essential major element for stony , shelled or tubed animals in our tank . When reading a mesaure of alkalinity we know how much it can buffer acid but also get a good read on how much carbonate we have since carbonate alkalinity typically makes up about 97% of the total alkalinity measurement.
der_wille_zur_macht
Team RC
An oldie but goodie:
http://www.advancedaquarist.com/2002/11/chemistry
IMHO this is one of the best practical guides to calcium and alkalinity in reef tanks. It describes what you need to measure, and what you need to do to correct your parameters if they are not in the ideal range.
This article dives a bit more into the chemistry end of things, along the lines of Tom's posts:
http://reefkeeping.com/issues/2002-04/rhf/feature/index.php
http://www.advancedaquarist.com/2002/11/chemistry
IMHO this is one of the best practical guides to calcium and alkalinity in reef tanks. It describes what you need to measure, and what you need to do to correct your parameters if they are not in the ideal range.
This article dives a bit more into the chemistry end of things, along the lines of Tom's posts:
http://reefkeeping.com/issues/2002-04/rhf/feature/index.php
der_wille_zur_macht
Team RC
To be more specific, overdosing can cause calcium carbonate to precipitate. The worry here is that if you are dosing an alkalinity supplement out of proportion to a calcium supplement, spiking the alkalinity too high can cause your calcium levels to plummet - your alkalinity might be fine because you're dosing "too much" of it, but corals will be unhappy with calcium being so low. This is not very likely with limewater, but with limewater, it's very hard to dose "too much" calcium or alkalinity without causing a dangerous pH spike.
Which brings us back to what IMHO needs to be the real emphasis here: Test your system for pH, calcium, and alkalinity, and don't dose anything unless you understand two things:
1) Are your current values appropriate?
2) Exactly what will your proposed dosing do to all three values?
No you don't want to dose as much as possible. It should not be used to control ph although it does effect it.
High dosing means skating the edge of a precipitation event which can drop alk precipitously and harm corals. While more alk may encourage more stony coral growth it also encourages abiotic precipitation and in some corals burnt tips and other problems have been noted. It is key to keep alk constant and above 7dkh
Recommended ranges for alk which is your surrogate measure for carbonate is : 7 to 11 dkh,.
To convert this to meq/l or ppm : 1 meq/l equals 2.8 dkh and 1 meq/l equals 50ppm. So ,at 7 dkh you have 125ppm of alk (97% of which is carbonate/bicrbonae).At 11dkh , you have 11dkh divided by 2.8= 3.9meq/l x 500= 196ppm. Natural seawater at ph 8.2 has roughly 110 ppm bicarbonate and 20 ppm carbonate; roughly 7dkh or 2.5meq/l.
