Correct way of taking water sample

[reefplayer]

Hi all,

I have been wondering on many occasion on the correct way of taking water sample during test. As we are aware there are so much water in our tank, but which part of the water column we need to take for water test?

I heard that taking water sample from high flow and surface area will have less NO3 but lower water column like near sandbed will have higher NO3. Is that true? Pls advise?

[nyfireman3097]

very good question like to know the awnser to thins myself
Nick

[reefplayer]

Maybe someone like Alex or Bob can answer that.

[Aged Salt]

Hi Stanley, I take my samples 2" below the water surface from my sump area, as it's closest to my testing area.[I try to keep my hands out of the water as much as possible] You could test your N03's from both sample areas mentioned to see if it's signicantly different, but Salifert's undetectable limits the absolute result. Bob

[Aquatic Image]

With the amount of water flow most of us have in out tanks I do not see it being possible to get different readings taken from different areas of the tanks. But I guess I could be wrong, not likely though

[nyfireman3097]

is there any type of diffrence taking from the sump or the tank ?
Nick

[G.Alexander]

Stanley, all I can tell is, water from the surface contains more nutrients. This is why I keep my water sample to measure PO4 in the middle of the tank where strong current is present. This can also be done with a tweezers, because the skin from your hand also leaches PO4.

Ca, Mg and KH water samples are also taken not directly form the surface at a position in the tank where strong current is present.

I have all my technical equipment running in the sump (Ca reactor, skimmer, carbon etc) and I am sure there are fine differences in the parameters in comparison to the tank.

G.Alexander

[mesocosm]

Greetings All !

With the amount of water flow most of us have in out tanks I do not see it being possible to get different readings taken from different areas of the tanks.

While I generally agree with Dustin_Y, there are a few exceptions.

It might be worth noting that if you're taking samples from "mid-level" in the water column ... away from biologically active surfaces, and away from areas of rapid gas exchange ... the results should be very representative of the "overall" system.

It might also be worth noting that it depends of the variable being measured. The testing of a variable such as dissolved oxygen can be strongly influenced by where the sample was taken. On the other hand, a parameter such as temperature shows little "overall" variance in terms of sampling location ...

... unless it's from right on top of the heater ...

A variable where time of sampling comes into play is pH. When you take the water sample for a pH measurement can influence the result.

There exist a few "microclines" within our systems where the location of water sampling can yield skewed results. G.Alexander is definitely right about water sufaces ... the top 2-3 cm of the surface-water interface, particularly in proximity to strong current ripples, can produce slightly different results from samples taken 15-20 cm below the same point in the water column.

Other areas where skewed results are very possible are those within 2-3 cm of very biologically active surfaces. Samples taken within 2 cm of the surface of LR or an active substrate can yield unrepresentative results. Samples taken over 2 cm below the surface of an active substrate can yield very unrepresentative results ...

... but why would you take "general" samples from there?

Ever tried water sampling from within an active substrate? It is a MAJOR PAIN ...

...

I have been wondering on many occasion on the correct way of taking water sample during test. As we are aware there are so much water in our tank, but which part of the water column we need to take for water test?

Again, I generally agree with Dustin_Y ... given the "typical" flow rates through our systems ... with the exceptions of areas where powerful physical and/or biological processes are engaged ... our system's water is so well "mixed" that our results should be pretty representative.

It seems to me that if we're taking samples well below the surface of either the tank or the sump (>= 5 cm), we're getting representative results.

A greater concern to me (than where the sample is taken from) is the "error percentage" inherent to over-the-counter chemical titration test kits ...

...

JMO ... HTH ...

[nyfireman3097]

Helpful as always
Nick

[Diesel3443]

I knew Gary would chime in on this one He never lets me down

[Orion76]

A greater concern to me (than where the sample is taken from) is the "error percentage" inherent to over-the-counter chemical titration test kits ...

I was about to say, many hobby test kits probably aren't accurate enough to reliably indicate the subtle difference between sampling locations. In many cases they are only good for "detectable" and "undetectable".

It's probably only relevant if you are using a Hanna photometer, Merck Aquacant etc.