Prevent fresh saltwater precipitation during storage?

[jDoSe]

I have read a lot of salts precipitate out if you mix them for too long (even relatively low alk like tropic marin pro and seachem salinity). Many recommend you use the salt 2 hours after mixing.

I am wondering what exactly is in a tank that is not in a mixing bucket that prevents precipitation?

I have read it’s possibly phosphates, but is it that simple? If i add sodium phosphate and increase phosphate to maybe 0.05ppm, will it prevent all (most) precipitation?

 

[jeffww]

I store for up to a moth without issues. Don’t use a heater or electric pump long term in the storage tank as heat causes precip. Keep cool and aerate well before use. Some precipitates are expected on the walls of the container but ph and alk are typically within spec.

 

[jDoSe]

I store for up to a moth without issues. Don’t use a heater or electric pump long term in the storage tank as heat causes precip. Keep cool and aerate well before use. Some precipitates are expected on the walls of the container but ph and alk are typically within spec.

I know some are worse than others though. Some salts you can store for months and be fine, but some only last a few hours. From what i read, most that need to be used right away are the synthetic salts (tropic marin, seachem salinity, brightwell neomarine, etc), which are the ones i want to use.

 

[Randy Holmes-Farley]

Precipitation is more likely in higher alk mixes and at high pH and temperature.

So keep it unheated and do not try to raise the pH.

Phosphate will make precipitation less likely by contaminating the calcium carbonate crystals and preventing further growth.

The role of pH in phosphate inhibition of calcite and aragonite precipitation rates in seawater

Seeded growth experiments were used to investigate carbonate precipitation kinetics in natural seawater spiked with 5 to 100μmol/kg dissolved inorgani…

www.sciencedirect.com

Seeded growth experiments were used to investigate carbonate precipitation kinetics in natural seawater spiked with 5 to 100μmol/kg dissolved inorganic phosphate. Precipitation rates of calcite and aragonite were measured using a constant disequilibrium technique (pH-stat) (S = 35, 25°C, and 1 atm total pressure) at three CO2 partial pressures (10−1, 10−2, and 10−3.5 atm). Over solution pH values from 6.9 to 8.6, aragonite growth rates decrease with increasing PO43− concentration, whereas decreases in calcite rates are dependent on increasing concentrations of both HPO42− and PO43−.

 

[jDoSe]

Precipitation is more likely in higher alk mixes and at high pH and temperature.

So keep it unheated and do not try to raise the pH.

Phosphate will make precipitation less likely by contaminating the calcium carbonate crystals and preventing further growth.

The role of pH in phosphate inhibition of calcite and aragonite precipitation rates in seawater

Seeded growth experiments were used to investigate carbonate precipitation kinetics in natural seawater spiked with 5 to 100μmol/kg dissolved inorgani…

www.sciencedirect.com

Seeded growth experiments were used to investigate carbonate precipitation kinetics in natural seawater spiked with 5 to 100μmol/kg dissolved inorganic phosphate. Precipitation rates of calcite and aragonite were measured using a constant disequilibrium technique (pH-stat) (S = 35, 25°C, and 1 atm total pressure) at three CO2 partial pressures (10−1, 10−2, and 10−3.5 atm). Over solution pH values from 6.9 to 8.6, aragonite growth rates decrease with increasing PO43− concentration, whereas decreases in calcite rates are dependent on increasing concentrations of both HPO42− and PO43−.

Do you know what the phosphate level would have to be to make precipitation much less likely (they only give one number)?
Would anything else like nitrates have any affect?

 

[Randy Holmes-Farley]

Do you know what the phosphate level would have to be to make precipitation much less likely?
Would anything else like nitrates have any affect?

Organics can have a big effect (depends on the exact organic). Nitrate has no effect.

I kept my IO for a month or more, and I wouldn't/didn't add anything to it.

In the paper, 10 umole/kg had a significant effect.

10 umole/kg x 95 ug/umole = 950 ug/kg = 1 ppm

i do not know what lower limit would have a useful effect.

 

[Randy Holmes-Farley]

It may be counter productive, but you can likely stop precipitation by adding soda water (lowering pH) and certainly can by reducing alk and pH with a mineral acid such as muriatic acid.

 

[jDoSe]

It may be counter productive, but you can likely stop precipitation by adding soda water (lowering pH) and certainly can by reducing alk and pH with a mineral acid such as muriatic acid.

Yah i dont want to go that extreme. Just want to prevent as much as i can for a week. I think im going to add like .1ppm phosphate. Apparently seachem salinity is the worst one and that is what i am going to try.

 

[flyingscampi]

BRS tested stored saltwater mixes over a period of time in this video: