Liquid GFO...

[jason2459]

Hmm, the correlation to PH is interesting. I wonder if the anecdotal reports/speculation about kalk lowering phosphate has more to do with the PH of the tank, then with the fact kalk is being used? Because kalk will raise the PH of the tank, and some people have high PH values to start with, so their tank may be running at a PH level where calcium can play a noticeable part in binding PH whereas for tanks with naturally low PH, the kalk dosing does not move the PH into the range where significant calcium binding takes place.

The graphs in the article illustrated quite well that the binding that takes place which is being attributed to calcium starts with a modest effectiveness (~10%) around PH 8.00, but rises quickly to a point around 50% in the range of PH 8.4-8.5.

In any case, if I am binding phosphate, then I want it to be either inside a coral skeleton, or in a media that I can remove from the tank. Precipitating onto my rocks does not seem like a worthwhile plan.

Dennis

I don't see data points at 8.4 and 8.5. They mentioned ranges up to 8.5 and above 8 but specifically mentioned a marked increase in binding with Calcium ions above 9.0.

 

[dartier]

For the effectiveness at 8.4-8.5 range, I was simply using the chart (for the ground bentonite) and extending the point between 8.0 and 9.0 dashes ( for the mid point) to determine the percentage of effectiveness. It clearly peaks about 9.0 and 4.0 as the article states, but there is still a noticeable effect at PH levels that we would typically experience in our tanks.

I still have some bentonite at home stored away after my recent move. I think I will dig it out and mix up some solution to the same concentration as I previously used. Then I can test some tank water to see if the phosphate level does change. No plans to do any in tank testing though.

Dennis

 

[bertoni]

Calcium carbonate doesnt dissolve neyther in fresh water or saltwater.It has verry little solubility but when acid is added it will disolve.I live cloose to somme calcium carbonate mountains.They disolve a litle when it rains but thats because of acid rain.Normal fresh water doesnt dissolve it in the absence of co2 or of somme acid.CaOH and CaCl in my opinion are the best of the best in binding phosphates in saltwater.GFO and aluminium oxide granules falls on second place.LaCl is to treat swimming pools.

Here's a quote from the article you posted:

By adding small quantities of hydrochloric acid, which will decrease the pH, it is predicted that a greater quantity of calcium carbonate will dissolve in the water. Also, the second step of the reaction mechanism should become more rapid, thus also speeding up the final step. A maximal quantity of phosphate should also be removed with the lowest pH (Zumdahl, 2000).

The method they are using is to dissolve calcium carbonate in fresh water, perhaps with some acid to increase the dissolution and speed the reaction.

From:

http://www.advancedaquarist.com/2002/7/chemistry

the solubility of calcium carbonate in water with atmospheric levels of carbon dioxide is about 20 ppm Ca⁺⁺ and 2.8 dKH, or about 6 ppm and 1 dKH in without any carbon dioxide. Both numbers are high enough to support phosphate removal, if the reaction can occur at the pH, etc, in the water sample.

I'm still not clear on why you think calcium carbonate is better than GFO for removing phosphate. We all agree that phosphate can be adsorbed onto the rock surface. That's how live rock can end up leach phosphate into the water column: when the concentration of phosphate in the water column drop below equilibrium with the phosphate adsorbed onto the rock, the phosphate is released into the water column.

GFO clearly works to remove phosphate from tanks with a lot of calcium carbonate, and tanks with a lot of calcium carbonate can suffer from a lot of phosphate in the water column. I'm not sure what mechanisms you are trying to propose, but a little bit of measurement indicates that our tanks sometimes need GFO.

 

[jason2459]

Thanks. I appreciate clear and logical summary of your posts in this thread.

Mike

Sorry, I just saw this post to me as I was trying to recap many posts into yet another thread.

Thank you.

 

[2smokes]

Hmm, the correlation to PH is interesting. I wonder if the anecdotal reports/speculation about kalk lowering phosphate has more to do with the PH of the tank, then with the fact kalk is being used? Because kalk will raise the PH of the tank, and some people have high PH values to start with, so their tank may be running at a PH level where calcium can play a noticeable part in binding PH whereas for tanks with naturally low PH, the kalk dosing does not move the PH into the range where significant calcium binding takes place.

The graphs in the article illustrated quite well that the binding that takes place which is being attributed to calcium starts with a modest effectiveness (~10%) around PH 8.00, but rises quickly to a point around 50% in the range of PH 8.4-8.5.

In any case, if I am binding phosphate, then I want it to be either inside a coral skeleton, or in a media that I can remove from the tank. Precipitating onto my rocks does not seem like a worthwhile plan.

Dennis

Its exactly what i was saying that calcium works best at higher ph (like saltwater is) and GFO works best at lower ph-it was invented for fresh water that has lower ph than 7.To bond phosphate inside your tank it is a worthwhile plan because thats how reefs are build and all the rocks are a deposit of inorganic phosphate that only calcium can stop them from leaking.GFO cant go on the rock surface to stop it.This process of phosphates neutralised by calcium allready happens in every reef aquarium just for somme its verry hard to believe it

 

[jason2459]

Its exactly what i was saying that calcium works best at higher ph (like saltwater is) and GFO works best at lower ph-it was invented for fresh water that has lower ph than 7.To bond phosphate inside your tank it is a worthwhile plan because thats how reefs are build and all the rocks are a deposit of inorganic phosphate that only calcium can stop them from leaking.GFO cant go on the rock surface to stop it.This process of phosphates neutralised by calcium allready happens in every reef aquarium just for somme its verry hard to believe it

Not hard to believe that phosphates can bind to Ca. We believe it quite well and have stated so several times. However, using limewater to do this has a basis in theory but not applicable in practice.

If someone could somehow make this work I would love to see it. A reactor of some kind somehow. Not a kalk reactor as that's shown to not be effective at all in reducing and/or maintaining PO4.

I also see no reason to believe GFO is not effective in our saltwater aquariums. It has been shown time and time again to be very effective at reducing PO4. I don't know how someone can say it is not effective in seawater.

 

[dartier]

Hmm, not sure where my post went from last night about my test of calcium bentonite clay went? Weird. If you see some off topic post (from me) in another thread let me know where it landed. :lolspin:

In any case I can recap what I did and then provide the first result. I located the container of bentonite clay that I had used before. Only looked like 1 or 2 tablespoons of clay were missing, so I must not have used much previously.

I filled a 500 ML container with tank water and added 1/2 teaspoon of bentonite clay. I also measured the tank water's PO4 level (0.50 ppm) using a Salifert test. I mixed the sample and set it aside to settle out.

This morning the sample was completely clear, all the clay had settled to the bottom. First observation, the clay must expand its volume fairly significantly when hydrated. The bottom of the container had a layer that appeared to be at several times the volume of the 1/2 teaspoon of dry clay.

I decided to test the PO4 level even though it had only been 12 hours. The article I linked mentioned that bentonite did most of its binding in the first day, but was still capable of binding PO4 for up to 23 days. Ok, the sample was 0.50 when it was added and mixed with the bentonite ~12 hours ago. Today the sample tests 0.25 PO4 (using same Salifert test).

I have to confess I was a bit surprised at the result. I kind of expected 0.00 due to the ratio of bentonite to tank water used (500ML:1/2tsp). Even a 50% reduction in phosphate is a significant result though.

I will test the sample again tonight, and then hopefully once a day for the next several days to see if the bentonite continues to lower the PO4 in the sample.

Dennis

 

[jason2459]

Yes, the clay will absorb quite a lot. Interesting results. Will be hard to know what element in the clay bound the most PO4 but there's several that can work together.

 

[jason2459]

Found this analysis of a at least one source of calcium bentonite clay. Good food for sponges and diatoms. Minus some of the other elements and unknown trace elements.

https://www.google.com/url?sa=t&sou...CQGFDuFXx-jce0grQ&sig2=xEjdzMEuf4mxaIVrHVc3bA

 

[dartier]

The bentonite clay that I am using for the test is marketed as a detox bentonite clay / dietary supplement. I am just wondering if the metals in it would be as high in this clay (E.g. Aluminum Oxide) if it is supposed to be food safe? Although the 'S' word might nullify any expectation of safety (E.g. Supplement).

Dennis

 

[jason2459]

It is probably close to the same break down but hard to say based on where it's materials are sourced. That analysis was for supplemental use and noted as being generally safe by the FDA as are most supplements.

 

[dartier]

When I got home last night, I measured the sample with bentonite clay again. Got 0.25 again on the test kit. No change from the 12 hour mark.

This got me to wondering if the calcium bentonite would have different precipitation rates over straight calcium carbonate? So I went out and purchased some Now brand calcium carbonate powder and repeated the same test (500ML tank water, 1/2 tsp CaCO3). I tested the sample this morning (about 10 hours after mixing), 0.25. Hmm same result as the calcium bentonite clay. I also tested the bentonite sample this morning again. Same result as last night 0.25. I went back and tested straight tank water just to make sure that I was in fact starting with 0.50 PO4, and it again tested 0.50 on the test kit.

Tonight I will test against Iron Citrate solution. I will post my planned mixing ratio of the iron solution momentarily for feedback.

Dennis

 

[dartier]

Iron Citrate Solution ingredients (using Sodium citrate hydrate)

Iron Citrate Solution ingredients (using Sodium citrate hydrate)

I was not able to get Sodium citrate dihydrate and instead ended up with Sodium citrate tribasic hydrate. So I have altered from Randy's recipe which called for 50.7g of the dihydrate to use 44.4g of the hydrate version. Hopefully I have converted it in the right direction (less as opposed to more).

Here is my planned recipe

25g of Iron (II) sulfate heptahydrate
44.4g of Sodium citrate tribasic hydrate
250 ML RODI

For the chemistry inclined folk, please provide feedback if I have the recipe right for substitution of the hydrate version instead of dihydrate.

Dennis

 

[2smokes]

When I got home last night, I measured the sample with bentonite clay again. Got 0.25 again on the test kit. No change from the 12 hour mark.

This got me to wondering if the calcium bentonite would have different precipitation rates over straight calcium carbonate? So I went out and purchased some Now brand calcium carbonate powder and repeated the same test (500ML tank water, 1/2 tsp CaCO3). I tested the sample this morning (about 10 hours after mixing), 0.25. Hmm same result as the calcium bentonite clay. I also tested the bentonite sample this morning again. Same result as last night 0.25. I went back and tested straight tank water just to make sure that I was in fact starting with 0.50 PO4, and it again tested 0.50 on the test kit.

Tonight I will test against Iron Citrate solution. I will post my planned mixing ratio of the iron solution momentarily for feedback.

Dennis

Try to bake really hard the CaCO3 powder then soak it in fresh water then after it stops from boiling ,test it.

 

[dartier]

I went ahead and mixed up a solution as mentioned 2 posts above. Randy calculates that this solution has 5g of Iron II in the total volume of 250ML. My plan was to create another sample of 500ml of tank water and add enough of the Iron Citrate solution to get a noticeable decrease in PO4. I decided to try to dose the proper amount to achieve 0.15 ppm, which is the upper limit of what GlennF warns not to exceed.

Lets see if I did this right ...

5g in 250ML = 5000 mg in 250ml = 5000/250 = 20 mg/ml

1 ML added to 500ml(sample) = 20 mg/500 = 0.04 mg/ml

So I added 3 ml of the Iron Citrate solution to the 500ml which if my calculations are right should be 0.12 mg/ml.

Hmm, I think I missed my target as it should have been 0.15 mg/L not 0.12 mg/ml. Good thing I am doing these tests outside of a tank!

Hmm, let's see if I can figure out what I should have dosed in 500ml to equal 0.15ppm or .15 mg/L ...

Ok, I think I should have added 0.15ppm/20mg = 0.0075ml (of 20mg/ml) ... but we are actually talking about 500ml, not 1L, so 0.00375ml of the 20mg/ml solution, which if I am right this time should be 0.15mg/L or 0.15 ppm.

So I exceed the intended dose by close to 1000x (3ml > 0.00375ml) ... assuming I got it right this time ...

Dennis

 

[dartier]

OK, I measured the PO4 in the sample using the Iron Citrate.

As I later determined that I had used way, way more iron citrate than needed in this sample, I expected that there would be excess iron. The sample has a distinct yellowish green tinge to it. Most likely from the excess iron used.

I was concerned that the precipitated phosphate may be picked up by the test, so I filtered the test sample through a coffee filter before running the test kit on it.

The results of the phosphate test read 0.0 PO4. Not a even a tinge of blue. that being said, the test sample still had a distinct yellow colour to it. Like really old tank water.

The fact that the test read 0.0, was both great, and expected. I later calculated the 3ml of iron citrate that I added to the 500ml sample, should have been enough to take 100G to 0.159ppm of iron. By my calculations this put the iron citrate sample at about 120mg/L of iron. So massive overdose in the test sample and no PO4 detectable as a result.

Dennis

 

[dartier]

I was thinking, it would be cool to see if the iron citrate sample could be used to precipitate out more PO4 in one of the other samples (bentonite or CaCO3). So I measured the Po4 in the CaCO3 sample, it is now lower than 0.25, but not quite 0.1, so it is still precipitating PO4. The fact the precipitation is still progressing might confuse the test. I measured the bentonite sample, 0.25, perfect. The bentonite sample is either not precipitating still or it is doing it very slowly. I added 1ml of the iron citrate sample to the bentonite sample. If the bentonite sample precipitates more, than this will confirm my earlier observations and also that the iron citrate sample had a massive excess of iron. I expect that the 1ml of the iron citrate sample I added to the bentonite sample, should raise the iron level to 0.12ppm less whatever was used initially by the Po4 in the iron citrate sample. Clear as mud?

Dennis

 

[dartier]

Try to bake really hard the CaCO3 powder then soak it in fresh water then after it stops from boiling ,test it.

Hmm, does not sound too applicable to what to expect from actual use in a tank. At least if I understood you correct, bake the CaCO3, add it to the sample, and when the sample stops boiling, test the sample? I will stick to using the CaCO3 at room temperature with CO2 level at equilibrium.

Dennis

 

[jason2459]

FYI, GlennF will bring iron levels to .25ml/l according to one post and his spreadsheet

Max .25 measured 1 hour after dosing. And according to another post he sees the iron precipitate out what it will after 6 hours.

 

[dartier]

FYI, GlennF will bring iron levels to .25ml/l according to one post and his spreadsheet

Max .25 measured 1 hour after dosing. And according to another post he sees the iron precipitate out what it will after 6 hours.

Thanks. I was going based on his Phosphate page on his DSR site. I do not want to get in trouble, nor get Glenn in trouble, so I will not post the link. You can Google "reef dosing iron DSR phosphate" to find it. He goes through some of the chemistry on that page.

Ok, time to test the bentonite sample that I added 1ml of the Iron citrate sample to. I will post the results shortly.

Dennis