Can lanthanum drop phosphate below 0.10 ppm?

[Miami Reef]

I took an about a liter of tank water. It measured 0.18 ppm PO₄ and 8.8 dKH.

I added a few granules of lanthanum chloride. It was definitely overdosed compared to standard tank doses.

There was a lot of clouding. Almost looked like magnesium hydroxide precipitates. I used my magnetic stirrer to heavy mix the solution for 30 seconds, then I used a 0.44 um syringe filter to filter the samples prior to testing.

The results? 0.00 ppm PO₄ and alkalinity around 5 dKH.

I don’t know what this means, but I just wanted to share.

 

[Garf]

I took an about a liter of tank water. It measured 0.18 ppm PO₄ and 8.8 dKH.

I added a few granules of lanthanum chloride. It was definitely overdosed compared to standard tank doses.

There was a lot of clouding. Almost looked like magnesium hydroxide precipitates. I used my magnetic stirrer to heavy mix the solution for 30 seconds, then I used a 0.44 um syringe filter to filter the samples prior to testing.

The results? 0.00 ppm PO₄ and alkalinity around 5 dKH.

I don’t know what this means, but I just wanted to share.

Can you check the DKH? I think excess lanthanum precipitates lanthanum carbonate.

 

[Miami Reef]

Can you check the DKH? I think excess lanthanum precipitates lanthanum carbonate.

I did. It dropped from about 8.8 dKH to 5.3 dKH.

I was thinking of using lanthanum chloride to regenerate GFO.

 

[Dan_P]

I took an about a liter of tank water. It measured 0.18 ppm PO₄ and 8.8 dKH.

I added a few granules of lanthanum chloride. It was definitely overdosed compared to standard tank doses.

There was a lot of clouding. Almost looked like magnesium hydroxide precipitates. I used my magnetic stirrer to heavy mix the solution for 30 seconds, then I used a 0.44 um syringe filter to filter the samples prior to testing.

The results? 0.00 ppm PO₄ and alkalinity around 5 dKH.

I don’t know what this means, but I just wanted to share.

Lanthanum carbonate precipitation would lower alkalinity. I don’t think the lanthanum cation can interfere with the alkalinity test.

 

[Randy Holmes-Farley Verified Community Expert]

Lanthanum can certainly drop phosphate below 0.1 ppm.

 

[JGT]

I took an about a liter of tank water. It measured 0.18 ppm PO₄ and 8.8 dKH.

I added a few granules of lanthanum chloride. It was definitely overdosed compared to standard tank doses.

There was a lot of clouding. Almost looked like magnesium hydroxide precipitates. I used my magnetic stirrer to heavy mix the solution for 30 seconds, then I used a 0.44 um syringe filter to filter the samples prior to testing.

The results? 0.00 ppm PO₄ and alkalinity around 5 dKH.

I don’t know what this means, but I just wanted to share.

Uhhh, didn’t you do exactly that?

 

[Garf]

I did. It dropped from about 8.8 dKH to 5.3 dKH.

I was thinking of using lanthanum chloride to regenerate GFO.

I think GFO gets coated in a calcium carbonate, which will absorb/ desorb phos with lanthanum additions reducing it on the surface. I'm not sure this would be any more effective than a calcium carbonate, unless GFO has a larger surface area, which it may. Personally I'm regenerating calcium carbonate with sodium hydroxide and sodium chloride, once a week.

 

[Miami Reef]

I think GFO gets coated in a calcium carbonate, which will absorb/ desorb phos with lanthanum additions reducing it on the surface. I'm not sure this would be any more effective than a calcium carbonate, unless GFO has a larger surface area, which it may. Personally I'm regenerating calcium carbonate with sodium hydroxide and sodium chloride, once a week.

You aren’t using lanthanum anymore?

 

[Garf]

You aren’t using lanthanum anymore?

Not for a few months. Dunno if my tank is consuming more phos, or if the sodium hydroxide/salt regen combo is as effective, or my feeding regime change has made a difference (more herbivore pellets). I did try a session of three weeks of not regenerating and the phos increased as expected. My wife's yellow tang is the healthiest fish I've ever seen, even if small, tbh. Phos hangs around 0.3ppm (Hanna)

Edit - for what it's worth, when cleaning the sand, I smash it around a bit. Maybe this physically dislodges the contaminated surfaces leaving new substrate. I have not measured the before and after weights of my sand, I'm not a total weirdo, so my mom tells me.

 

[Miami Reef]

I’d like to do an experiment with spiking a beaker of tank water with 0.50 ppm PO4 and 10 dKH. I’d calculate how much of a lanthanum stock solution would drop phosphate by 0.45 ppm. I’d then like to measure the alkalinity and phosphate to see the affinity lanthanum had for each.

I think that would be interesting. What do ya’ll think?

 

[Randy Holmes-Farley Verified Community Expert]

One issue is going to be : how do you know there are not small particles of lanthanum phosphate suspended in the water that get into a phosphate test, and dissolve under the acidic conditions.

 

[Miami Reef]

One issue is going to be : how do you know there are not small particles of lanthanum phosphate suspended in the water that get into a phosphate test, and dissolve under the acidic conditions.

Because I already dropped 0.18 ppm phosphate with lanthanum in a beaker from the test in the first post. I got 0.00 ppm, which means the 0.44 um filter was effective at removing all of the precipitants.

 

[Randy Holmes-Farley Verified Community Expert]

Because I already dropped 0.18 ppm phosphate with lanthanum in a beaker from the test in the first post. I got 0.00 ppm, which means the 0.44 um filter was effective at removing all of the precipitants.

True. I'm just noting it as a limitation.

FWIW, in the deep ocean, lanthanum and phosphate are saturated and phosphate limits the available lanthanum concentration.

https://www.sciencedirect.com/science/article/abs/pii/0016703793903643?via=ihub