Randy Holmes-Farley
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My Tank Thread
Someone asked for a DIY lanthanum dosing recipe.
Be sure you understand that some folks have issues with fish (especially tangs) before embarking on lanthanum dosing.
it is also preferable to catch as many of the solids that precipitate out as you can, so dosing before some sort of mechanical filtration is desirable. Many folks use a filter sock.
Finally, note that lanthanum dosing will tend to drop alkalinity a bit, both from binding phosphate and from forming some lanthanum carbonate.
OK, so here's the rationale...
Lanthanum precipitates phosphate as LaPO4. Thus, each one lanthanum ion will remove one phosphate ion (ignoring lanthanum that ends up in other compounds, such as lanthanum carbonate, bound to organics, or remains dissolved in the water).
One phosphate weighs 95 grams per mole
One lanthanum weighs 139 g/mole
Thus, one mg of lanthanum ion removes 0.68 mg of phosphate.
I was asked to use lanthanum chloride heptahydrate ( Lacl3 7H2o; mw 371.5 g/mole) ) to make the dosing solution.
That material is 37% lanthanum by weight.
Dissolve 9 grams (~2 level teaspoons) of lanthanum chloride heptahydrate in water to make 500 mL total.
That solution contains 6.7 grams/L (3.33 g/500 mL)of lanthanum, or 6.7 mg/mL.
Let's pick a dosing volume of 1 mL, so we are dosing 6.7 mg of lanthanum, which will remove 6.7 x 0.68 = 4.6 mg of phosphate.
If that is added to an aquarium that has a total volume of 100 L, then we will be expecting to remove about 4.6 mg/100 L = 0.046 mg/L (~0.047 ppm) of phosphate.
Remember that due to binding to rock and sand, and release from that reservoir when you try to lower phosphate, one may see phosphate come back up close to the starting point within a day or two after dosing, and lowering phosphate can be a lengthy process.
Be sure you understand that some folks have issues with fish (especially tangs) before embarking on lanthanum dosing.
it is also preferable to catch as many of the solids that precipitate out as you can, so dosing before some sort of mechanical filtration is desirable. Many folks use a filter sock.
Finally, note that lanthanum dosing will tend to drop alkalinity a bit, both from binding phosphate and from forming some lanthanum carbonate.
OK, so here's the rationale...
Lanthanum precipitates phosphate as LaPO4. Thus, each one lanthanum ion will remove one phosphate ion (ignoring lanthanum that ends up in other compounds, such as lanthanum carbonate, bound to organics, or remains dissolved in the water).
One phosphate weighs 95 grams per mole
One lanthanum weighs 139 g/mole
Thus, one mg of lanthanum ion removes 0.68 mg of phosphate.
I was asked to use lanthanum chloride heptahydrate ( Lacl3 7H2o; mw 371.5 g/mole) ) to make the dosing solution.
That material is 37% lanthanum by weight.
Dissolve 9 grams (~2 level teaspoons) of lanthanum chloride heptahydrate in water to make 500 mL total.
That solution contains 6.7 grams/L (3.33 g/500 mL)of lanthanum, or 6.7 mg/mL.
Let's pick a dosing volume of 1 mL, so we are dosing 6.7 mg of lanthanum, which will remove 6.7 x 0.68 = 4.6 mg of phosphate.
If that is added to an aquarium that has a total volume of 100 L, then we will be expecting to remove about 4.6 mg/100 L = 0.046 mg/L (~0.047 ppm) of phosphate.
Remember that due to binding to rock and sand, and release from that reservoir when you try to lower phosphate, one may see phosphate come back up close to the starting point within a day or two after dosing, and lowering phosphate can be a lengthy process.
