Citric Acid to clean phosphates off old rock?

[Enderg60]

I saw someone recommend a 3%(by weight) citric acid bath to "unbind" phosphate from old live rock that was leaching phosphates into the water with the following source provided.

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

Has anyone tried this?

 

[Randy Holmes-Farley Verified Community Expert]

Like any other acid, citric dissolves the surface of the rock and will help remove phosphate. There’s nothing special I. This regard by using citric.

 

[Enderg60]

So not much different than a regular muriatic acid bath? Just eats off the outer layer that had phosphate bound in the new growth?

 

[Randy Holmes-Farley Verified Community Expert]

So not much different than a regular muriatic acid bath? Just eats off the outer layer that had phosphate bound in the new growth?

I do not know of any reason to think it is different.

There is no interaction whatsoever between citrate and phosphate itself that would effectively lower the phosphate concentration in the water, unlike the interaction between citrate and calcium, where the way that citrate is especially good at dissolving calcium carbonate is chelation of the calcium by citrate.

 

[Enderg60]

My understanding dropped with every comma in that last sentence.

Follow up question. If I want to remove the phosphate tainted layer of rock thats 10+ years old would you recommend an extra round or two in the acid bath?

 

[Randy Holmes-Farley Verified Community Expert]

My understanding dropped with every comma in that last sentence.

Follow up question. If I want to remove the phosphate tainted layer of rock thats 10+ years old would you recommend an extra round or two in the acid bath?

Two treatments for old rock that has a history of exposure to high phosphate are:

1. Soak in salt water that you keep adding lanthanum too, removing the phosphate fromt eh rock and precipitating lanthanum phosphate.

2. An acid soak, stripping asway the outer layer of the rock. Lots of bubbling. Do it outside.

As a different treatment, bleach would be used to remove dead organic matter, but do not mix the bleach and acid at all. Mixing them together can create toxic chlorine gas.

 

[Enderg60]

Ive already done 7 days in 10% bleach, 24 hours in prime, 24 hours in fresh, then 24 hours in 10:1 muriatic acid and a last 24 hours in fresh before drying again.

I was planning to do the cure in saltwater with lanthanum until it stops leaching before use. Im a little concerned about how much time it will take for the rock to stop leaching so if a second acid bath would help now is the time to do it.

 

[Enderg60]

but do not mix the bleach and acid at all. Mixing them together can create toxic chlorine gas.

Thankfully I know this, but more thankfully I noticed a storage mistake before something bad happened. A good example of how easy it can be to make fatal mistake.

 

[trevorhiller]

Sounds like overkill to me. The muriatic acid is going to do exactly the same thing as the citric acid-only much faster and to a greater extent.

If you’re really that concerned about phosphates leaching, why not just run some Rowaphos on the new system from the get go? The lanthanum chloride should precipitate the phosphate from the water, but I don’t know about the rocks. The Rowaphos will continuously absorb them and is probably more effective.

Seems to me that they are going to absorb some phosphates though from the addition of fish food unless you run Rowaphos 24/7 and keep the levels at zero so this all might be overkill.

just my opinion

 

[Enderg60]

The system this rock came from a system that ran for 10 years and I could never get the phosphates under 0.8 even using tons of GFO, and a scrubber. Id like to reuse most of the rock, but Im not going to introduce a known problem to a new system.

 

[Dan_P]

The system this rock came from a system that ran for 10 years and I could never get the phosphates under 0.8 even using tons of GFO, and a scrubber. Id like to reuse most of the rock, but Im not going to introduce a known problem to a new system.

Just wondering how successful your cleaning procedure has been tothis point. Did you place a piece of rock in saltwater to see if there was any phosphate stillleaching?

 

[Enderg60]

Rock is currently dry, I was planning to start cycling it next weekend. I have some more rock that needs an acid dip so nows the time.

The reason im concerned is while the acid dip removed a decent layer off the surface I still see a lot of old growth on the rocks that could potentially be phosphate laden.

 

[doubleshot00]

Ill give my 2 cents on this as i did nothing but bleach my dry rock and put it in the tank. I took 4-5 months for the rocks to stop leaching. But i also used rowaphos 2 months after the cycle was finished. So ran rowaphos for 3 months. I check phosphates 2x a week to stay on top of it.

 

[Enderg60]

Thanks, Thats good info!

Do you remember what the phosphate levels were at when you started? Did they stay at that level most of the time or did it start to fall off evenly?