GFO vs Lanthanum Chloride for phosphate control/removal

[FrugalReeferJon]

I've used GFO my entire reefing career but am thinking about trying out lanthanum chloride. Frankly, I'm getting tired of the messiness when I have to replace my GFO. Discussions are welcome and encouraged (reasoning, advantages, disadvantages, etc).

 

[slingfox]

GFO absorbs some trace elements. LC does not but likely requires more careful dosing if you have tangs.

 

[FrugalReeferJon]

GFO absorbs some trace elements. LC does not but likely requires more careful dosing if you have tangs.

I read that LC, theoretically, can bind with other elements.

 

[slingfox]

I read that LC, theoretically, can bind with other elements.

Here is what the AI overlord states:

In reef aquariums, lanthanum chloride (LaCl₃) is primarily used because the lanthanum ion (La³⁺) forms an extremely insoluble precipitate with phosphate:

But phosphate is not the only thing it can interact with.

Other ions and compounds lanthanum can bind or precipitate with include:

• Carbonate (CO₃²⁻)
  Lanthanum readily forms lanthanum carbonate. In seawater, carbonate concentration is much higher than phosphate concentration, so some lanthanum gets consumed this way. This can slightly reduce alkalinity if dosing aggressively.
• Bicarbonate (HCO₃⁻)
  Indirectly involved because bicarbonate equilibrates with carbonate in seawater chemistry. Lanthanum can shift this balance and contribute to alkalinity reduction.
• Hydroxide (OH⁻)
  Lanthanum hydroxide can precipitate, especially in higher-pH microenvironments.
• Silicate (SiO₄ species)
  Lanthanum can bind silicates to some extent, though much less strongly than phosphate. Some wastewater applications use lanthanum for silicate removal.
• Organic molecules / dissolved organics
  Lanthanum can associate with negatively charged organic compounds and particulates. This is usually a minor pathway but contributes to floc formation.
• Suspended particles / detritus
  The precipitates formed with phosphate and carbonate tend to aggregate with fine particles, which is why mechanical filtration is important during dosing.

What it does not strongly bind in normal reef conditions:

• Nitrate
• Ammonia
• Calcium
• Magnesium
• Sulfate
• Chloride

Practical reef-tank implications:

• Alkalinity can decline during heavy lanthanum dosing because some lanthanum reacts with carbonate species.
• The white cloudiness sometimes seen is often a mix of lanthanum phosphate + lanthanum carbonate particulates.
• Free lanthanum and fine precipitates can irritate fish gills, especially tangs, if not filtered through a fine mechanical filter (commonly 5–10 micron socks).
• Because carbonate competes strongly, lanthanum dosing becomes less efficient at very low phosphate levels.

Compared with GFO, lanthanum chloride is generally:

• More efficient for large phosphate reductions
• Cheaper at scale
• More likely to affect alkalinity and create particulate irritation if overdosed or poorly filtered

 

[exnisstech]

I've always been afraid to use LC because of the reports it can harm tangs. True or not I have tangs that are 8 & 9 years old so I'm just not willing to risk it.
I agree with the mess and time needed to rinse GFO and it's why I don't bother running it unless my Hanna ULR tester is flashing 0.9 and then I'll usually run some.

 

[dwest]

Worried about tangs here too. My purple is over 30 years old.

I use GFO in a cheap bag from Amazon that I run under my skimmer outlet and replace every 3 weeks. I used to run a “reactor” but that way was messy. But the bag works ok for me.