Rock leaching phosphates?

[Hodge1995]

I was wanting some knowledge from the water chemistry gods. If live rock gets full enough of phosphates to start leaching it back into the tank what are the remedies? Will it continue to leach until it is empty or just to a point that it is for lack of better terms "happy".

[aaroz]

Hey Hodge

Water chemistry god, er no, still learning and will still be when im retired! Fairly knowledgeble well i kinda have to be to do my job, so i hope so

Rock, especially Calcium Carbonate (live rock) that has been in water that is high in inorganic phosphate will adsorb phosphate, the depth and level of contamination will depend on a varietty of factors for example, length of time of exposure, properties of the carbonate structure and concentration of exposure.

Eventually at some point an equilibrum will establish and phosphate leaving the rock will equal phosphate entering, because phosphate leaves the rock we reefers can remove it.

If we remove the phosphate from the water column then it will continue to leave the rock, the length of time this takes is dependent on the factors described above, however, at some point the rock will low enough in phosphates, and if you provide other essential parameters including enough good light, watermovement, correct temperaure, correct salinity and a balanced supply of calcium and carbonate you will get the calcerous growth most reefers aim for (bascically phosphate inhibits biological and abiotic precipitation of calcium carbonate).

In a good reef <0.05mg/l of phosphate is usually barely detectable but most find that <0.1mg/l is sufficient to see a massive improvement!

Now there are various methods of removal but the ones I personally always reccomend to those who are not hydrochemists or uber reef geeks are GFO (granular ferric oxide) and Kalkwasser. GFO a black-brown granular substance can be used in a canister filter, special reactor or i have even myself just added direct to aquaria and syphoned out after a few months. Figures for phosphate removal are from the water column and not from an aquaria. Depending on your phosphate levels you may need a large dose and change it often.

Kalkwasser (calcium hydroxide) is a more long term and maintanance solution and should be added dissolved as part of evaporation topoff water (just follow instructions on the box) add morning and/or night because it sequesters CO2 from the water forming Carbonate, thus raising the pH of your aquaria. Some or much of the kalkwasser (depending on the chemistry of the aquaria) this forms Calcium Carbonate this acts as a further sink for excess phosphate and can also be removed by syphoning during water changes. Kalkwasser is fantastic for helping to keep on top of phosphates in the long run as well as providing some balanced Calcium and carbonate and pH stability amongst others, add daily, slowly to replace evaporated water and keep any eye on the pH in the beginning

Other parameters are important... What is the Calcium, kH, and Magnesium levels in you aquaria? Also although Nitrate is difficult to measure accuratley and not the evil beast it is often made out to be it can often be a good indicator for further action.

[bertoni]

Kalk might remove phosphate from the water column by precipitating calcium phosphate, but that's never been shown to happen. The carbonate has little to nothing to do with phosphate removal.

If you keep the phosphate level in the tank at your target level for long enough, the rock eventually will be depleted of phosphate, although that can take a while.

What is the level in your tank now? Or is this more of a curiosity question?

[Hodge1995]

Well I have a 300 dt. I bought some second hand live rock about 1 1/2 years ago when I got into saltwater. Not knowing any better I did not cook it or anything of the sort. I fought water parameters for at least 6 months before I got it under control. For the past year everything has been ok until I recently got a GHA outbreak. I went at it by reducing light time , gfo in a dual brs reactor with the second running carbon and still doing my regular 75 gallon WC every 2 weeks . The tank went from a disaster to not to bad in about 2 weeks.I do have some algae still a was trying to get an idea how long it would leach . I am 90% sure it is a live rock issue due to the fact I don't have many fish and coral and don't feed much at all. I am on vacation currently and don't have my testing result in front of me to give exact numbers but They all were within range but I am assuming that the phosphate is getting sucked up by the hair algae and now gfo and therefore testing good. I had never run gfo before and wasn't sure of what result I will get in the long run. I guess the main reason for the question was that I wanted to make sure I wasn't delaying the inevitable of a full tank shut down and cooking rock.

Sorry for the long reply and thanks for your guys input.

[bertoni]

Well, there are a number of ways to proceed. Personally, I wouldn't break the tank down. I might try removing as much hair algae as is easy to get (if any, in that size tank), spending a few minutes a week, and just run some GFO for a while first. That's easy to do, and might help a lot. AlgaeFix might, as well.

If that failed, I might remove the corals and fish for a bit, and use a lights-out treatment to kill the hair algae. That could be followed by a treatment to remove the phosphate (maybe just water changes with perhaps some lanthanum chloride).

[aaroz]

[QUOTE=bertoni;21759028]Kalk might remove phosphate from the water column by precipitating calcium phosphate, but that's never been shown to happen. The carbonate has little to nothing to do with phosphate removal.
QUOTE]

J Bertoni this is getting slightly old, and you are so active on these forums it seems it is loss to the community that you are not aware of the full benefits of calcium hydroxide. It is so cheap and simple for those with less experience to use and will save many aquariums and dishartened aquarists IMO. Here are a few journals for you documenting the removal of phosphate from water with elevated PO4 using Calcium Hydroxide and Calcium carbonate.

http://www.sciencedirect.com/science...11916407008715

http://www.tandfonline.com/doi/abs/1...38149009354700

http://www.jstor.org/discover/10.230...21102514614437

If you are still in doubt try this a little desk top project... Airate some calcium hydroxide solution with extra solids until the pH is stable at around the 8.2 mark (all CaOH had become fairly pure CaCO3) add precipitate into some water with an elevated (and known) phosphate level. Let the precipitae fully clear from the water column and then measure Phosphates again.... What do you think now?

If an aquariums water column has a PO4 level of 1mg/kg it is much much higher in the carbonate rock /kg.... I will dig out a journal i have somewhere with the details if you wish.

Hilsen

Aaroz

[bertoni]

I agree that Kalk can be used to treat wastewater. I don't see how that applies to a reef tank. This article might help:

http://reefkeeping.com/issues/2005-01/rhf/index.htm#15

[aaroz]

Randy Farley was a real inspiration to me when I first started out, he writes well and in a clear format that is easy to understand. One of the things I best respect about him thou is his ability to state when he does not fully understand. He is thou like any researcher a man who is not always right, like me, like you like us all here.

I cannot tell you in absolute and intricate details of what heppens to each and every calcium and hydroxide ion when it enters a reef aquarium. I can tell you thou that not eash and every calcium and carbonate ion dissolves into solution, the percentage will vary with method of dosing, and the existing water chemistry.

This relativley pure calcium carbonate WILL attract phosphates ontop its surface, just like every calcium carbonate structure in a reef aquaria. This effect is ofcourse limited by the addition of kalkwasser which in turn is limited by evaporation or pH.

Just try that simple experiment that I suggested, I have dropped the phosphate levels in 2000L live rock holding systems by the addition of airated kalkwasser aka calcium carbonate powder!

I'm not saying it is easy to quantify, i'm not saying it is a stand alone solution but i am saying it is an effective, cheap, simple long term aid in the fight we reefers and professional aquarists alike have against rising phosphate levels in enclosed saltwater systems.

[aaroz]

Ps Bertoni.. I snipped this this from that article article you suggested....

"An alternative mechanism for phosphate reduction via limewater may simply be the precipitation of calcium phosphate, Ca3(PO4)2"

And

"As with the precipitation of CaCO3 containing some phosphate, if these calcium phosphate crystals are in the water column (e.g., if they form at the local area where limewater hits the tank water), then they may become coated with organics and be skimmed out of the aquarium."

Not sure about the skimmer bit (maybe some) but becoming part of detritus sounds more reasonable to me.

[blanden.adam]

Alright guys, this fight about the quantitative role of calcium hydroxide's effect on phosphate in a reef aquarium has been going on long enough and I agree it is getting tiresome. I will propose an experiment to address the issue to see if it is acceptable to the community to quantitatively address the issue.

I will take 3 500mL beakers and fill them with artificial seawater taken from my aquarium at my next water change. It will be tested at that time for specific parameters, but roughly they will be

(all mixed from reef crystals)
s.g. 1.026 (atc refractometer calibrated to 1.0264)
alk: 8.6 dKH (saliftert test kit)
cal: 450 ppm (salifert test kit)
mg: 1450 ppm
phosphate: 0.00 ppm (hannah checker)
ammonia/nitrate/nitrite: undetectable by API test kits

To that I will add sodium phosphate buffer at pH 8.3 to set the phosphate level at 0.10 ppm (by hannah checker). Then, under continuous stirring, I will add 5 mL of saturated limewater in 5 equal doses of 1 mL added slowly spaced evenly across 24 hours. I will do this for 3 days, and then measure the phosphate of each beaker. Is this an adequate experiment to address the issue?

Oh, and of course at the end the final volume will be made up to 500mL with the addition of water.

[aaroz]

Sure, why not!
5 ml reprasents 1% volume, probably 24hours evaporation from an average aquarium.

Add Sodium Phosphate before you separate into beakers (easier and way more precise) actual figures are less important here than change relative to a control test where you must add pure water alone. Remember repeats aswell.

Well done for making the effort Adam!! Good luck

[Hodge1995]

I for one would like to see the results. If I decide to go to kalkwasser is there a chart to decide on dosing amount.Is there any downside to dosing this stuff. My calcium levels are always on the high side, I would assume that the kalk would raise it even more. Just to add I am always having to dose alk. but never calcium.

Latest parameters:
Ammonia , Nitrite , Nitrate, phos all 0
Alk 7.8
Calcium 490
MG 1500

I am assuming there has to be some levels of phos and or nitrate with the GHA outbreak

[blanden.adam]

I must propose some minor revisions to the experiment because of practical concerns:

First, instead of 5 equal doses of 1mL, I will dose 6 equal doses of .84 mL (peristaltic pump doses at 0.028 mL/min according to my calibration run, timer turns on in 30 minute intervals, so it works out nice and even that way).

The second is that I will do 3 trials in series rather than in parallel because of my inability to find more of the tubing that goes to said pump.

I will not report any results until the experiment is complete so proper statistics can be done. Is the experiment still acceptable to everyone involved?

[bertoni]

I think my point has been that there's no evidence that Kalk precipitates phosphate, especially in any appreciable quantity. That quote goes back to Randy, who, in the article, talks about the hypothesis that Kalk removes phosphate. He's very clear there, and in his posts in this forum, that there's no evidence that it does.

If you want to post your opinion that limewater does remove phosphate, that's fine, but I think you should at least label your opinions as such, and stop complaining when I post that you have no evidence for your point of view. This is supposed to be a science-based forum.

There are plenty of tanks that get limewater and still have phosphate problems, so whatever the effect might be, limewater is not a miracle cure for our tanks.

Dosing lime powder into a tank, as you've done, might be a lot more effective than dosing limewater in removing phosphate, but that's not what people are doing in this thread and the others where we've been discussing this issue.

[aaroz]

Ok just once more...

Phosphates adsorb into calcium carbonate, that is scientific fact, it is why phosphates linger so long in aquaria. Kalkwasser adds a relativley pure form of Calcium and carbonate (after the OH ion binds to a CO2 molecule) that eiter remains ionised or precipites, wether it precipitates abiotically, or biologically does not matter it will at some point adsorb phosphates. Not to a massive degree and maybe not enough in a heavily stocked tank to keep on top of it fully but constantly daily and relentlessly depending on evaporation rates.

I have never added Calcium Hydroxide directly to an aquaria, that is IMO not a good idea for the health of livestock! It is Calcium Carbonate powder (Hydroxide that has been reacted with atmospheric or artificial CO2).

Any how i put all this forward with the best intentions when it starts to make sense just spread the word so more can use the benefits of kalk it is in general highly underrated IMO!

[blanden.adam]

Idk if you can justify the statement that kalk is underrated, or that the word is not out about it. It's one of the "big three" calcium and alkalinity supplementation schemes (kalk, two part, and calcium reactor), and I see threads about its use in the RC chemistry forum daily.

I do not disagree that phosphate adsorbs to calcium carbonate, so the proportion of the kalk that precipitates as such does have the ability to bind phosphate, and if removed later will lower the phosphate in a reef aquarium to some degree. However, the issue is whether or not that amount is significant. I disagree with your assertion that biotically precipitated calcium carbonate will do the same thing as it is covered in coral flesh and has a relatively small surface area compared to calcium carbonate suspensions and live rock/sand, and even if it were true then kalkwasser still would not have an advantage over any other supplementation scheme. (and unfortunately, there is no easy way to actually test your assertion unless someone wants to go dunking large quantities of stony coral in high phosphate water).

All that said, I would point out that there is a ton of abiotic calcium carbonate in a reef aquarium already (sand and rocks), and any amount added from precipitation is miniscule relative to the amount already present, particularly considering that when done properly, precipitation represents only a very small fraction of what actually happens in reef aquaria.

To demonstrate this, let's do some math. Let's take my aquarium for example, and only consider the dosing done via kalkwasser. There is 75 gallons of water volume, and every 14 days I add about 32 gallons of saturated limewater via my ATO. This means that per day, if 100% of the limewater precipitated as calcium carbonate, we get about 20 grams of precipitated calcium carbonate, which would show up on heaters, pumps, sump walls, etc. If what you say is true about calcium carbonate precipitation being a process that happens to a good proportion of the calcium hydroxide, let's say 30% just as a reasonable number, this would mean after a year I'd have 2.2 kg of abiotically precipitated calcium carbonate in my aquarium. This would take up about 1 L of space in the aquarium, and it would be absolutely plain to the naked eye. Clearly such precipitation is not happening, and even if it did, my rocks and sand would still be more than 15-times the calcium carbonate added via the kalk.

Now, calcium carbonate as a powdered suspension (such as you made when aerating the calcium hydroxide) might be an entirely different story. Now you are talking about a lot of surface area that can adsorb phosphate, and is one of the methods used in medicine and water treatment for phosphate binding. I don't know the amount you would need to add or the most effective or safest implementation scheme would be, but there might be something to that. HOWEVER, you need to differentiate these two processes in your mind and in your recommendations. When people on the forum are talking about kalkwasser, they are usually talking about it as calcium hydroxide for supplementation of calcium and alkalinity. When YOU are talking about kalkwasser, you are consistently talking about it as already-reacted to pure calcium carbonate, and as a phosphate reducing mechanism. These are entirely different things, and should be kept separate.

[bertoni]

Originally Posted by aaroz

Phosphates adsorb into calcium carbonate, that is scientific fact...

I think most everyone in the conversation understood this a long time ago. You ignore the real issue at hand, which is whether the amount of phosphate that dosing Kalkwasser will remove is significant.

[tmz]

Originally Posted by blanden.adam

Alright guys, this fight about the quantitative role of calcium hydroxide's effect on phosphate in a reef aquarium has been going on long enough and I agree it is getting tiresome. I will propose an experiment to address the issue to see if it is acceptable to the community to quantitatively address the issue.

I will take 3 500mL beakers and fill them with artificial seawater taken from my aquarium at my next water change. It will be tested at that time for specific parameters, but roughly they will be

(all mixed from reef crystals)
s.g. 1.026 (atc refractometer calibrated to 1.0264)
alk: 8.6 dKH (saliftert test kit)
cal: 450 ppm (salifert test kit)
mg: 1450 ppm
phosphate: 0.00 ppm (hannah checker)
ammonia/nitrate/nitrite: undetectable by API test kits

To that I will add sodium phosphate buffer at pH 8.3 to set the phosphate level at 0.10 ppm (by hannah checker). Then, under continuous stirring, I will add 5 mL of saturated limewater in 5 equal doses of 1 mL added slowly spaced evenly across 24 hours. I will do this for 3 days, and then measure the phosphate of each beaker. Is this an adequate experiment to address the issue?

Oh, and of course at the end the final volume will be made up to 500mL with the addition of water.

Hi Adam,

I think calcium phosphate is likely to form at some level along with calcium carbonate .Will the strirring occur in a sealed container? The other question is will it be exportable from the aquarium and how,ie, the mechanism for export or will it remain indefinately as precipitant. In your proposed experiment will any calcium phosphate influence the sample used for a Pi test?

[tmz]

J Bertoni this is getting slightly old,

I don't think Jonathan is getting old. Dismissive insults like that usually provide a transparent mask for a weak mind pretending to be more than it is.

[tmz]

Watewater chemistry is intersting to a point. The extrapoltions to living reef tanks are are usually off the mark and go on down the drain. The studies cited in your post are a case in point.. You can do lot's of things to wastewater that you can't do to a living tank.

[tmz]

The Op is concerned about caldium carbonate in his tank holding PO4 and leaching it back. How would adding more calcium carbonate surfaces be any different?

In your initial post you seem to be recommending dosing kalk at levels that encourage precipitation. Not a good thing in my opinion; don't know where the reaction stops and starts and it voids to an extent he primary purpose of the dosing which is to provide calcium and carbonate alkalinity for biotic calcification.

I've been dosing kalk 24/7 for about 7 years. It's a great calcium and alkalinity supplement . I like it's self purifying and pH raising qualities. If it precipitates
PO4 that is somehow exported that's a plus. It may or may not but if it does it's not very significant in my experience . Of course, I don't don't enough to encourage a biotic precipitation to clog pumps ,fouls heater's and such. Why would calcium carbonate precipitated form overdosed kalkwasser be any more effective at adsorbing PO4 species than substrate or rock surfaces or calcium carbonate formed from overdosing calcium chloride and carbonate for that matter?

[blanden.adam]

Hey Tom,

In the proposed experiment, the beaker would be open to the atmosphere and continuously stirred to simulate a reef aquarium with high flow. There would be no mechanism of export from the beaker, so any precipitate that formed would simply remain as a precipitant. The final water sample would be taken from the water at the top of the beaker and no pre-treatment would be given to the sample to liberate phosphates bound to the surface of any precipitates, so that fraction shouldn't be represented in the test results.

However, after looking over my own protocol, I'm beginning to wonder if the experiment is worth doing considering some of the claims being made. First, the Hannah Colorimeter I would be using is only accurate to +/- 0.04 ppm phosphate, so any change would have to be rather significant for it to pick it up. Secondly, there are no calcifying organisms in the beaker, so the limewater dosed would just cause calcium and alkalinity to rise, which may give an inflated estimation of precipitation (but the temperature would also be slightly lower, so who's to say), and the 3rd and perhaps most damning issue is that Aaroz claims that biotically precipitated calcium carbonate serves as a phosphate binder like abiotic calcium carbonate does, and I have no intentions of taking any of my stony corals and subjecting them to high phosphates in a closed system just to prove a point. So, alas, perhaps such a reductionist approach is inadequate :/, and true experimental aquaria would be required to address all of the issues at hand scientifically.

[Allmost]

Originally Posted by tmz

J Bertoni this is getting slightly old,

I don't think Jonathan is getting old. Dismissive insults like that usually provide a transparent mask for a weak mind pretending to be more than it is.

lolol I didnt read that as Jonathan getting old

subject of that sentence is "this"

but yea he should have used correct grammer lol

for the OP : "If live rock gets full enough of phosphates to start leaching it back into the tank what are the remedies? Will it continue to leach until it is empty or just to a point that it is for lack of better terms "happy".

Live rock is calcium carbonate and can bond to po4. it doesnt actually get "full" but rather its dependant on the water it is in. if po4 on rock is 0.01 nad po4 of water is 0.001, the rock will give off po4 untill po4 of rock = po4 of water column.

by that explanation, best way to remove it, is to continouly remove po4 from water column.
I personally do not like kalk as way of controlling po4, as you do not remove any po4 ... you just bond it and let is settle ... it can be released later on and cause algae.
Use Fresh live rock, and if live rock is old or has po4, maybe Lacl might help, or acid washing it.

HTHm,

[tmz]

Adam,

Thanks for the reply. I think the stirring open to the air would encourage precipitation including some calcium phosphate as the CO2 and oxide would from carbonate and then calcium carbonate a biotically along with some measure of calcium phosphate at the .1 level but I don't know that for certain or whether the calcium carbonate formed would absorb significant levels of Pi . I think you are right that a reef aquarium would likely behave differently via biotic precipitation including some Pi as well CO2 variations from photosynthesis and other activities. I think th amount of Pi sunk in skeletal mass would depend on the amount of Pi in the water vs the amount of available carbonate. Then there's the potential for organics in the aquarium to bind up some of calcium phosphate too.

I wonder if just keeping calcium high would enocurage more calcium phosphate precipitation overall?

[tmz]

lolol I didnt read that as Jonathan getting old

That's technically correct. I chose not to repeat the entire text but if you go back and read it the intent is pretty clear