Most human-readable phosphate test kit?

[bertoni]

So by the same logic.... if you have a sample that you dilute by a factor of ten of DI water, then again you may not have enough reagent.

Not quite, because DI doesn't contain any reactants. Also, the usual approach is to test the normal amount of total water.

The issue with using 10 times the tank water sample and the normal amount of reagents is that the water might have more chemicals that will react than reagents available. So your approach might work, or might lead to an underestimate of the amount of phosphate.

 

[Randy Holmes-Farley]

I don't see why it should matter how much water is in the way

It does. It is the amount of colored reagent/phosphate combo per volume of water that is what you observe. Put the same color reagent/phosphate combo in more water, and it looks less colored and will match a lower concentration on the card or wheel or whatever you are comparing to.

 

[Bob 1000]

I like the Martini photometer by Milwalkee.. Hands down it's the best tester I have.. and reads faster than a hanna.. I have tested it against 2 hannas and it read more consistant than both. They both got 2 separate readings from on sample.. and my martini cost less.. I have kept sps reefs for the past 5 years with a total of 13years in the hobby..

 

[Av8bluewater]

Yeah.. the cheap test kits are made for "high range". They do make low range test kits but they're like $50-60 so might as well buy a photometer.
I have the Hanna Instruments Photometer and it is the way to go.
If you don't have a way to test low range you could be throwing out GFO media too soon or not soon enough. So I figure it pays for itself.

 

[PowermanKW]

I don't see why it should matter how much water is in the way

It does. It is the amount of colored reagent/phosphate combo per volume of water that is what you observe. Put the same color reagent/phosphate combo in more water, and it looks less colored and will match a lower concentration on the card or wheel or whatever you are comparing to.

OK, that makes sense, but the API color chart changes to different colors. So while the diluted sample will be a lighter color as you point out, the shade is still the same shade.

 

[PowermanKW]

Not quite, because DI doesn't contain any reactants. Also, the usual approach is to test the normal amount of total water.

The issue with using 10 times the tank water sample and the normal amount of reagents is that the water might have more chemicals that will react than reagents available. So your approach might work, or might lead to an underestimate of the amount of phosphate.

I get what you are saying, but I already know my level is low because I test. I'm not say do it this way always.

I test my water and it comes out as zero. Well....is it zero, is it .1 is is .2???? The next gradient is .5 and even that color is not much different than the zero color.

So, lets find out. I do my ten times test and it shows a perfect color change of 2. So it is .2. OK.... well.... it is zero, .2, .3, .1. How accurate does it need to be? What I know is that it is very very low. .2-0.

If the test has enough reagent to test up to 10, then I still have plenty to react. Obviously if it registered a 10, then I could certainly be over that, but I'm at zero, not at 10.

Even still....10 is way high and off the scale. Bad stuff. But is it 15-20-25? Well what do we do, we dilute with water. Perfectly acceptable. I don't see what the difference is.

When we do our water chemistry at our plant, it is perfectly acceptable practice to do this. Because we could be out of range of our probe or test and whether we do hand tests or grab samples in an analyzer seems reasonable to me.

 

[Av8bluewater]

Do yo mean .02? .. .2 is very high.
I don't see how adding 10X the water would work.

 

[PowermanKW]

Do yo mean .02? .. .2 is very high.
I don't see how adding 10X the water would work.

I mean .2

How do you even measure .02???

The first one away from zero on my chart is .5

 

[bertoni]

The Hach kit measures down to about 0.03 ppm phosphate.

If you're sure that the water is low in phosphate, then the extra reagents might not be needed. I'll defer to others on that subject.

 

[Av8bluewater]

I mean .2

How do you even measure .02???

The first one away from zero on my chart is .5

Those are high range charts. They're actually useless unless you have a real PO4 problem.
In order to read low enough you need a low range test kit or a photometer. I measure on the Hanna Instruments photometer.
Generally corals will stop growing at .1 (that may vary from coral to coral .. Phosban recommends <.015
http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=8996)
For best color of SPS you need to get down below .04 -.05 ish.
Mine has been around .02-.05 lately.
I was out of town for a week and had to set up the autofeeder with flake food.. and I saw it creep up when I came back.

 

[recife111]

The best test kits for po4 is Tunze and Merck,
Very easy to read.

I highly doubt you will need anything better.

 

[Av8bluewater]

The best test kits for po4 is Tunze and Merck,
Very easy to read.

I highly doubt you will need anything better.

Yeah, that merck was the one I was trying to think of.
http://www.aquabuys.com/page/aqb/PROD/dd_phosphate_test
Might as well buy a photometer though.

 

[PowermanKW]

Those are high range charts. They're actually useless unless you have a real PO4 problem.
In order to read low enough you need a low range test kit or a photometer. I measure on the Hanna Instruments photometer.
Generally corals will stop growing at .1 (that may vary from coral to coral .. Phosban recommends <.015
http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=8996)
For best color of SPS you need to get down below .04 -.05 ish.
Mine has been around .02-.05 lately.
I was out of town for a week and had to set up the autofeeder with flake food.. and I saw it creep up when I came back.

Wow thanks. I see people post and I seem to remember it is in the tenths. I have read other recommendations that below 1 is fine. That stunted growth does not happen till a couple of ppm.

Mine has always tested zero, but as I said what is "zero". I have good growth and color. My cheato in the fuge barely grows. I just figured I was good. I figured a phos reactor was not needed. Perhaps I should get a "real" small scale test and actually see what it is.

Thanks for setting me straight.

 

[Randy Holmes-Farley]

So just so everyone reading this thread understands the issues relating to test kits and volumes, I thought I'd summarize them here.

There are basically two types of test kits we use.

The first type are titration kits, where you use a fixed amount of tank water and add more and more of some particular reagent until you get to a color change. In short, you are adding a reagent that is altering something that is colored, and when you get to the point where you’ve added the same amount of reagent as the ion of interest in the tank water, you reach the tipping point in a color change (the exact nature of what is dong what changes by what ion we are talking about).

For our uses, these include calcium, magnesium, and alkalinity kits, and maybe others. In this type of test, you may be able to increase the precision somewhat by increasing the volume of the tank water. You will then need to add more of the titration reagent (and any other reagents needed) before you get to the endpoint, but as long as you can make it out clearly, this method will give good results. So, for example, in an alk kit where 1 drop equals 1 dKH, if you use twice as much tank water, then 1 drop equals 0.5 dKH, etc.

The second type of kit requires a fixed amount of tank water, a fixed and excess amount of reagent, and then the reagent combines with the ion of interest to form a color, with more color forming indicating more of the initial ion. You then compare the color to a card, wheel, etc. More and more color, and sometimes changing the apparent tint as well, indicates more and more of the ion of interest. This type includes most kits for ammonia, nitrite, nitrate, phosphate, iodine, and others. In this case, using more tank water cannot be used to give any improvement to the test results. What you can do, and some kits take advantage of, is look through a longer length of fluid made the exact same way, but possibly scaled up to make more, if necessary. That multiples up the apparent color of the sample. The Hach phosphate kit does this for low range.

 

[Randy Holmes-Farley]

I get what you are saying, but I already know my level is low because I test. I'm not say do it this way always.

It just never works to scale up just the water in a phosphate test. I'm sorry this is hard to understand, but concentrating the sample works, while scaling up the water and reading through the same length of water cannot (whether you use enough reagent or not). Increasing the volume of water does not change the amount of colored complex along the viewing path.

 

[PowermanKW]

I get what you are saying, but I already know my level is low because I test. I'm not say do it this way always.

It just never works to scale up just the water in a phosphate test. I'm sorry this is hard to understand, but concentrating the sample works, while scaling up the water and reading through the same length of water cannot (whether you use enough reagent or not). Increasing the volume of water does not change the amount of colored complex along the viewing path.

No, I understand reagents and amounts of ions, but after Av8tor put a light bulb over my misunderstanding, then I had to do some reading.

And I understood what you meant by looking at a longer view of result, but I realize how important that is in this case better now. And no the tests I do at the plant are not color tests, so they are not the same. Sorry it took so long with the light bulb, and I certainly didn't mean to hijack the thread.

 

[Randy Holmes-Farley]

No problem.

Happy Reefing.

 

[2thdeekay]

I compared API, Salifert, and Merck(DD) kits, along with the Hanna low range meter. Wish I had the Hach to compare, but don't.

I like the Merck kit. The sample tubes are nice & long, making it easy to read--you compare the test sample and blank till they match in amount of blue color along the color card. Less than $100 for the kit, and refills are ~$45 for 100 more tests, I think.

I really like the Hanna meter, which seems to give similar results/numbers as the Merck, but more convenient to read a number vs. reading color comparison. Initial outlay is more, but refills are cheap.

Salifert is ok, but harder to read. Sample length is pretty short. As Randy says, it really helps to have a longer length of sample to intensify the color from the blue phosphomolybdate complex. Salifert's sample size is 10 ml's in the short vial behind the colorcard.

API is calibrated for too high a range, and is useless for reefing purposes, imho. PO4 can be off the chart for the Merck/Hanna, while API reads zero. :hmm5:

I have a question about the Merck PO4 kit. The color card is calibrated for both phosphorus and phosphate in ppm. The phosphomolybdate method measures PO4, where P is a calculated %. Did they add the calibration for P just to make the kit appear to be more sensitive than it really is? Many folks (including vendors) don't know the difference, and 0.008 mg/L sensitivity for a PO4 test kit is quite impressive, but maybe a bit confusing.

 

[PowermanKW]

I would like to get the Merck kit if it is worth the money. After I figure out where I need to go and get control I don't see me testing all the time. I would just hate to be running around doing stuff and not being able to measure results. The Hanna meter is expensive and +/- .04 is sort of a large error range considering how low we are trying to measure.

 

[recife111]

The merck kit is very good, Tunze po4 kit is just as good as the Merck kit
They are made by Macherey-Nagel

The Hannah meter is ok, but these test kits are easier to use.