# Question re. CSM+B precipitate



## adechazal (Nov 12, 2008)

I've done some reading in this Fertilizing forum that seems to confirm my experience; while using CSM+B I get a precipitate in the water column (slightly cloudy) but what's more frustrating is I also notice an orange residue in my sump and in the filter media when using the CSM+B, is this normal?

My tank is a well lighted and heavily planted 180g and I had been using 1/2 tsp of CSM+B each day for five days of the week. I've since dropped this back to 1/4tsp per day to try to cut back on the orange residue in the sump and filter media but at this level I don't know that I'm supplying enough Fe.

So my questions are:
1. Is the orange residue a sign that I was using way too much CSM+B?
2. Should I get Fe from some other source
3. Anyone know if the iron chelate from aquariumfertilizer.com is DTPA or EDTA?
Aaron


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## goldier (Feb 13, 2010)

The orange residue is excess iron. You need not add more CSM+B as it has iron in it. The chelating agent from aquariumfertilizer.com is EDTA.

http://www.aquariumfertilizer.com/index.asp?Option1=inven&EditU=2&Regit=5


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## Philosophos (Mar 1, 2009)

1/2 teaspoon is enough to be non-limiting. It's something like .25ppm. You can tweak that with other iron sources or increase the dosing to provide for luxury uptake as an added advantage, but it's not necessary for healthy plants.

CSM+B is loaded with Fe EDTA, which disassociates at a much faster rate above something like 6.5pH. You'll sometimes get disassociation resulting in precipitates from having fairly hard water. The other big cause, and the one that I think may be your problem given the dosing schedule, is combining the stuff with most PO4- related compounds. FePO4 forms and precipitates right out of the water as it is insoluble. In short, try changing your dosing of macros/micros to separate days. 

If that doesn't fix it, 4L flourish costs about $50 to ship to your door, which at most will dose 40 gal of column of mid to high tech for a year. For that price, you might as well just get some ADA AS (ADA AS I if you're big on maxing nutrients for the substrate, AS II if you don't want tannin staining a day or two after WC and don't mind a bit of sacrifice) and be able to dose CSM+B which costs about $20 to mix up 8-9 gal of stock solution that will dose roughly 3x as much into your tank as minimum flourish dosing.

Just throwing stuff out there. I've worked the numbers over more than once on this one. 

The orange thing is weird; it may be the iron. I haven't encountered it so I can't comment really.


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## goldier (Feb 13, 2010)

Philosophos said:


> CSM+B is loaded with Fe EDTA, which disassociates at a much faster rate above something like 6.5pH.


I think you meant it the other way around? In high pH, EDTA (an acid) is deprotonated and therefore tightly bound to cations (Fe and other metals) to form complexes.

I also think that the cloudiness is from the binding of Fe (the excess in the water) to PO4. It just seems a lot to dose daily with the micros. Plants don't need a lot of these, and sometime they take a little rest from growing.


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## adechazal (Nov 12, 2008)

Thanks Goldier and Dan, I'll stick with 1/4 tsp 5x per week and see how things go. Do you know if the Fe 10% chelate from aquariumfertilizer.com is EDTA or DTPA? I know the CSM from them is EDTA but I'm not sure about the straight Fe. I sent them a message but haven't received a response. 

Apparently the GLA Fe is DTPA and I see from some posts on this topic that DTPA may be a good alternative.

Oh, also wanted to note that I dose macros at 6:00am and CSM at about 5:00pm, so there is some separation but not 24 hours worth.

Aaron


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## Philosophos (Mar 1, 2009)

It definitely breaks down in higher pH ranges:

http://www.barrreport.com/showthread.php/6930-How-long-iron-gluconate-quot-live-quot-in-tank?p=46515#post46515

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VC2-494HP3F-3&_user=10&_coverDate=12%2F31%2F2003&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1263795515&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ef2f8df5e9ee22273d4ec677aed62f12

http://en.wikipedia.org/wiki/Equilibrium_constant#Competition_method

The last link explains it best, but I won't go claiming that I understand the math.


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## Philosophos (Mar 1, 2009)

Oops, sorry adechazal; looks like you posted while I was still typing.

You can reduce the quantity if you like, but if you're dosing it along side KH2PO4 it's going to keep precipitating.

They no longer carry the 10% DTPA as far as I know; it's all 13% EDTA. I'm looking for another source myself; combining multiple chelates is a nice way of doing things


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## wet (Nov 24, 2008)

goldier,

Please correct me.


> In high pH, EDTA (an acid) is deprotonated and therefore tightly bound to cations (Fe and other metals) to form complexes.


But if that bond is too strong we even titrate Fe out of solution, yeah? For our purposes in solution I think we're targeting that range where micronutrients (Fe and other metals) have a stronger affinity for the chelator (EDTA or otherwise) than to oxidize out of our target state (Fe+2 to Fe+3).

The coloration and haze from different chelators in solution doesn't seem to just be percipitate with Fe and PO4 (you'll see the coloration when adding the chelator to DI water, for example) but at least in part to that chelator dissolving in water.

adechazal,

It's normal to see residue or coloration from different micronutrients does dry. In my tanks, Cherry and Amano shrimp, Otos, and Rubbernose and Bristlenose plecs eventually eat that stuff after it gets a little furry. Have you thought about leveraging your sump into a refugium? This can be cheap with some lights (say, spiral CFL in a desklamp) and floating stems (faster uptake, less mess and easy trims by removing stems) or epiphytic plants (Anubias, mosses, etc. Can be pretty.) Sump can be easier to maintain with no substrate but that is also an option, of course. The idea here is the CSM+B will have some stuff to settle on as it dissolves and you get the bonus of additional uptake. Regardless adding some critters above will help.

(Sumps are cool. FW fuges are super cool.)

I have seen very dark spots when dry dosing large amounts of either CSM+B or DTPA chelated Fe into my 6dKH water that settle down before dissolving. If you get around to it, see what dosing concentrated (not high dilution) traces from a syringe looks like -- you'll find it is heavier than water and you can squirt bits of into into plantings or carpet where it will settle down. The idea here is to keep the settled spots away from the glass and target dose.

Minor quibble: if you are going to regularly dose micros -- which is smart in, at the least, using brute force to ensure regular input at your target levels -- you might want to think about dosing it in the morning and macros at night. A more efficient way when assuming the tank is inefficient 

I think your levels are good especially with high light and uptake (stems), fwiw.


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## goldier (Feb 13, 2010)

I see Dan. I didn't think about the OH- at higher pH when I looked at EDTA pKa (at most 2.69 for the acid tails) which is definitely lower than any aquarium water to guarantee a good EDTA-Fe binding. The ScienceDirect article explained it well when EDTA-Fe complexes dissociate from neutral pH (7.0) and higher due to the competition of more available OH- in the water, and then form iron hydroxide. Iron hydroxide can be oxidized further and precipitates into color orange.

http://www.chemguide.co.uk/inorganic/transition/iron.html (colours of iron hydroxide)
http://en.wikipedia.org/wiki/EDTA (EDTA properties)

So Adechazal, if your pH is within the range as shown in Tom's graph where the curve drops rapidly, and with heavy dosing of CSM+B, I think the orange residue of iron hydroxide is what you would see.



> But if that bond is too strong we even titrate Fe out of solution, yeah?


Wet, Yes. But slowly so as to hold Fe hostage, and to render Fe not become quite reactive for a while. Eventually the strong bonds b/w EDTA-Fe break down (i.e. degradation of the acid under light, EDTA-Fe dissociation constant rises at pH 7 or higher), then Fe is released and becomes free for plants to use.


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## adechazal (Nov 12, 2008)

Goldier, I'll bet you're right about the iron hydroxide (basically rust right?) My pH is just above 7 before CO2 turns on and just under at the end of the day so I'm in that steep curve range that Tom's post depicted.

I can't imagine that iron hydroxide is useable by the plants so my non-chemically based thinking suggests it's simply going to waste e.g. that .25ppm I'm supposed to be getting by dosing 1/2tsp is going to be something less than that, perhaps much less? I have no idea. Seems like picking up some DTPA from GLA might make for a good experiment.

Wet: thanks for the refugium idea for the sump, hadn't thought of that but for now I'll just try to keep one set of plants alive.

And thanks Philosophos and Goldie for answering the question about aquariumfertilizer.com's EDTA chelated Fe.
You people are out of control! In a good way. Thanks so much for the help.
Aaron


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## nfrank (Jan 29, 2005)

> -- you might want to think about dosing it in the morning and macros at night.


i dose both at the same time of the day.... first the macros and then the micros... one after the other. I could do the opposite if there is a good reason. Once these ferts mix in the large volume of tank water and their concentrations are greatly diluted, i can't see how there is much of a problem for the PO4 to react with Fe.... or visa versa.

Think about it this way: when you dose into the main aquarium, there is already Fe and PO4 present. I think (but have not confirmed) that the precipitate only forms when the concentrations are high enough... like in a stock solution.

I have had a FW refugium style sump since i set up my new tanks... and love it. Poret sponge does the filtration and provide dividers. The sump is wonderful place to keep extra plants, shrimp, and without my choice -- a place for fry to develop.


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## goldier (Feb 13, 2010)

adechazal said:


> Goldier, I'll bet you're right about the iron hydroxide (basically rust right?) My pH is just above 7 before CO2 turns on and just under at the end of the day so I'm in that steep curve range that Tom's post depicted.
> 
> I can't imagine that iron hydroxide is useable by the plants so my non-chemically based thinking suggests it's simply going to waste e.g. that .25ppm I'm supposed to be getting by dosing 1/2tsp is going to be something less than that, perhaps much less? I have no idea. Seems like picking up some DTPA from GLA might make for a good experiment.


Yes, rust basically, on land is iron oxide, a dehydrated form of iron hydroxide in water environment. All have similar orange/red color.

Aaron, plant roots' enzymes can break down the iron hydroxide residue and absorb iron, but it looks like the flakes all end up in places other than the substrate. Since your pH is around 7, DTPA would give you a margin of about 1 pH higher, as seen from Tom's graph. I would give DTPA a try.


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## wet (Nov 24, 2008)

That's true about Fe and P, Neil, especially in Aaron's 180g + Sump. My suggestion was to think of time Fe stays available vs time plants photosynthesize if Aaron wants to split micros and macros up for whatever reason. 

Aaron -- you should also check out NFrank's pics of his "new Pearl Grass" emergent, too, to maybe push you over the edge or get you brainstorming. I understand your wanting to focus on the main tank -- smart. But remember the sump/fuge doesn't have to be pretty yet and can hold plenty of plants. More plants almost always help


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## Philosophos (Mar 1, 2009)

If you work from stock and wait a few minutes between dosing, odds are PO4 isn't going to be a huge deal. I've seen enough people doing it now that I would call it the exception.

On the other hand, dry dosing both at the same time may not play out so well. For that matter, dumping the two in side by side at the same time from stock may not be a bright move. I'm not sure though, testing that sort of thing in-situ isn't my idea of fun.

Personally I like to have a routine of opposite days. I rinse my graduated cylinder before and after use, reducing the risk of mixing residues.


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## nfrank (Jan 29, 2005)

> That's true about Fe and P, Neil, especially in Aaron's 180g + Sump.


My sump is partitioned into 3 compartments with Poret sponge. I always dump the macros into the compartment with the return pump and the micros into the other end of the 40gallon sump which holds about 30 gallons of water. I believe that the macros get mostly pumped up by the time the micros make it across to the other side.

If i dumped both in at the same end,and at the same time, then i might be seeing the same problem... except for the mulm at the bottom that would make it hard for me to see a brown sludge.


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## barbarossa4122 (Dec 31, 2009)

GLA sells DTPA. I got some last month.
http://www.greenleafaquariums.com/aquarium-fertilizers-supplements/iron-chelate.html


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