Phosphate leaching from live rock- best course of action?

[Tanster2]

Hi all,

I recently set up a Biocube 32. I had some old rock stored away from one of my other tanks, so I decided to use it. The rock was covered in grime and old, long dead life.

I bathed the rock in muriatic acid for about 15 minutes, but apparently that was not enough. I should've bathed for longer, and I definitely goofed here. The rock has been leaching phosphate for months, and I cannot get them under .25ppm. I'm keeping them maintained chemically, and with the use of a skimmer.

My question is, would you guys go ahead and remove the rock? It's been leaching for 3 months now and hasn't slowed down.

I could go ahead and change out the rock with new rock, and implement some seeding product to enhance bacteria growth on new rock. I also have plenty of bio media in back, so the new rock would be colonized quickly.

Anyone else had this issue? How did you resolve?

 

[jman930]

Following along because I have the same issue. Dumb question but related. Can rock leach nitrates as well?

 

[Tanster2]

Following along because I have the same issue. Dumb question but related. Can rock leach nitrates as well?

Good question! Typically no, phosphate is more easily absorbed and held by live rock in my understanding.

Hopefully others can chime in, but I haven't heard of rock leaching nitrate the same way it may leach phosphate.

 

[enderg60]

I fought it for years with massive amounts of GFO. For a smaller tank this is a much easier option.

The only real way to do it is cycle the live rock in a bucket or something and dump Lanthanum chloride in there twice a week to remove the phosphates from the water. And just keep doing it until the rock stops leaching, which could take a long time.

Honestly the easiest thing to do is get new rock.

 

[ichthyoid]

Nitrate is much more soluble than phosphate. As such a good soak in clean DI water will do.

Phosphate is known to react with the calcium on aragonite rock that we use. When that happens it becomes chemically bound to the rock’s surface and forms a hard stable material, calcium phosphate.

The best way to mitigate the issue, is to soak rock in a 3% solution (by weight) of citric acid for several hours.

Citric acid has an affinity for solubilizing the phosphate. Especially when bound to the calcite rock surfaces as calcium phosphate.

After the acid soak, pour off the liquid and rinse the rock thoroughly with clean water. The citrate formed by reaction of the citric acid is not very toxic, so any residue is pretty harmless. In fact, it’s great for GA clay soil.

https://www.researchgate.net/publication/325393319_Solubility_of_Phosphate_Rocks_in_Citric_Acid

 

[enderg60]

Oooooo Thats good stuff. If that works it might save a ton of rock I have!

 

[Tanster2]

Awesome, thanks!

That being said, I think my best course of action is simply to take the old rock out and replace it.