Chemists: Pellets Containing Calcium Phosphate

[Miami Reef]

I’m just curious, will foods containing calcium phosphate in the ingredients add a significant amount of phosphates to an aquarium?

TDO Chroma Boost has Calcium phosphate in the ingredients.

 

[Dan_P]

I’m just curious, will foods containing calcium phosphate in the ingredients add a significant amount of phosphates to an aquarium?

TDO Chroma Boost has Calcium phosphate in the ingredients.

You might grind some into dust and stir it overnight in some saltwater. Filter off the solid and test for phosphate.

 

[Slocke]

Calcium Phosphate is generally not water soluble. Which is good. I like how my bones don't dissolve in my rather damp body.

 

[Dan_P]

Calcium Phosphate is generally not water soluble. Which is good. I like how my bones don't dissolve in my rather damp body.

Makes one wonder why any phosphate exists in aquarium water with all the calcium in solution.

 

[Slocke]

Makes one wonder why any phosphate exists in aquarium water with all the calcium in solution.

I'm sitting with a chemist who when I asked him he disputed "a lot" and says that there is a lot more hydrogen carbonate then phosphate (I'm sitting at around 0.1ppm) thus why we have a lot of calcium carbonate in our reefs and not much Calcium Phosphate.

 

[Dan_P]

I'm sitting with a chemist who when I asked him disputed "a lot" and says that there is a lot more hydrogen carbonate then phosphate (I'm sitting at around 0.1ppm) thus why we have a lot of calcium carbonate in our reefs and not much Calcium Phosphate.

A lot of Ca++ which should minimize the amount of calcium phosphate that can dissolve which in turn means when phosphate is present should precipitate it.

 

[Miami Reef]

You might grind some into dust and stir it overnight in some saltwater. Filter off the solid and test for phosphate.

Won’t the pellet itself naturally contain phosphates?

So, the TDO chroma boost will add more phosphates (compared to other foods) or not? I’m kind of confused.

 

[Slocke]

Won’t the pellet itself naturally contain phosphates?

So, the TDO chroma boost will add more phosphates (compared to other foods) or not? I’m kind of confused.

Yeah. Instead get some pure calcium phosphate (or just some clean bone fragments) and test them in saltwater. Results should be minimal phosphate gain.

 

[Dan_P]

Won’t the pellet itself naturally contain phosphates?

So, the TDO chroma boost will add more phosphates (compared to other foods) or not? I’m kind of confused.

The funny thing about the label is that phosphorous is not listed in the analysis. I am pretty sure the pellets have phosphorous in addition to the little bit in calcium phosphate.

I would assume it will be a phosphate source

 

[EeyoreIsMySpiritAnimal]

@Reef Nutrition

 

[Randy Holmes-Farley Verified Community Expert]

Calcium Phosphate is generally not water soluble. Which is good. I like how my bones don't dissolve in my rather damp body.

FWIW, bones mostly aren’t exactly calcium phosphate, but rather a related compound, hydroxyapatite.

 

[Randy Holmes-Farley Verified Community Expert]

Won’t the pellet itself naturally contain phosphates?

So, the TDO chroma boost will add more phosphates (compared to other foods) or not? I’m kind of confused.

It may dissolve a bit, but I expect the amounts are low, especially relative to the large amounts of phosphate already in food.

 

[Randy Holmes-Farley Verified Community Expert]

Makes one wonder why any phosphate exists in aquarium water with all the calcium in solution.

Calcium phosphate is not typically at saturation in seawater, although I do not know if that applies to folks at high pH with phosphate > 1 ppm. So it can dissolve, but is probably slow and may get surface coatings of other ions on it that slow dissolution (perhaps mixed calcium and magnesium carbonate/phosphates).

 

[arnavfactoryfishtanks]

You've asked a great question about the impact of calcium phosphate in fish food on your aquarium's phosphate levels. Let's dive into some of the points brought up in the discussion and add some additional scientific context.

First, calcium phosphate itself is not very soluble in water. Its solubility is reported to be 0.002 g/L. This means that only a very small amount of calcium phosphate would dissolve in the water of your aquarium, and therefore contribute to the phosphate levels, under normal conditions.

Calcium forms ion pairs with various ions, including phosphate, which can lower the free concentrations of these ions in the water. Therefore, the presence of calcium phosphate in your fish food might not significantly increase the phosphate levels in the water. However, this does depend on several factors, such as the specific concentration of calcium phosphate in the food, the amount of food being added to the aquarium, and the overall water chemistry of your tank.

Normal phosphate levels in natural seawater are around 0.07 ppm, and for healthy coral, phosphate levels should be kept low, ideally around 0.020 ppm or less. Feeding your fish with food that contains phosphates could increase the phosphate levels in your tank. If you're noticing a spike in phosphate levels, the first place to look at is your fish food4.

It's also important to keep in mind that phosphate levels can be controlled with good export systems such as a quality skimmer or a refugium. Furthermore, switching to premium quality fish food free of unnecessary phosphates can help in reducing phosphate levels.

Therefore, while calcium phosphate in fish food could potentially contribute to phosphate levels in your aquarium, it is one of many factors that can influence these levels. Regular monitoring and adjustments of your feeding habits, water chemistry, and filtration system can help keep phosphate levels within the desired range.

Hope this helps!

And here's my sources I used:

Solubility table - Wikipedia

en.wikipedia.org

Chemistry and the Aquarium: Calcium

Randy discusses calcium and its role in helping maintain a healthy marine aquarium.

reefs.com

How Do Phosphates Affect My Saltwater Aquarium?

While phosphates don't normally affect the fish in your saltwater aquarium, elevated levels promote algae growth, and can affect your corals.

www.thesprucepets.com

Are Excess Phosphates Lurking In Your Fish Food | Reef Builders | The Reef and Saltwater Aquarium Blog

At one time or another, it seems like all aquarists deal with excessive phosphates in their tank. Phosphates could be silently lurking in your aquarium causing unsightly algae blooms…

reefbuilders.com

 

[Randy Holmes-Farley Verified Community Expert]

First, calcium phosphate itself is not very soluble in water. Its solubility is reported to be 0.002 g/L. This means that only a very small amount of calcium phosphate would dissolve in the water of your aquarium, and therefore contribute to the phosphate levels, under normal conditions.

Solubility in g/L in fresh water is not a good way to gauge if something will dissolve into a solution already containing those ions and which will be at a different pH.

 

[Dan_P]

Solubility in g/L in fresh water is not a good way to gauge if something will dissolve into a solution already containing those ions and which will be at a different pH.

Ksp of Ca3(PO4)2 ~10^-26.

I worked it out in my head that 400 ppm Ca converted to molarity and 1 ppm PO4 converted to molarity should precipitate. I am a fan of calcium phosphate dissolving in seawater.

At this moment I am writing a note to go through my reagents, find calcium phosphate, stir with Instant Ocean and measure the PO4.

 

[Miami Reef]

I am a fan of calcium phosphate dissolving in seawater.

Why are you a fan?

 

[Dan_P]

Why are you a fan?

Oh, just from the quick survey of how much it dissolves in water. I need to just make the observation in Instant Ocean to make sure this isn’t another Big Foot sighting.

 

[Randy Holmes-Farley Verified Community Expert]

Ksp of Ca3(PO4)2 ~10^-26.

I worked it out in my head that 400 ppm Ca converted to molarity and 1 ppm PO4 converted to molarity should precipitate. I am a fan of calcium phosphate dissolving in seawater.

At this moment I am writing a note to go through my reagents, find calcium phosphate, stir with Instant Ocean and measure the PO4.

It’s more complicated than that. Most phosphate in seawater at pH 8.2 is not PO4 - - - and doesn’t get counted in the ksp.

Also, ion pairing lowers the free phosphate a lot and lowers free calcium a bit.

 

[Randy Holmes-Farley Verified Community Expert]

Why are you a fan?

It will dissolve in normal natural seawater.