Controllers

[sagent3000]

is there a controller out there that will tell me all of the following

pH
Temp
Calcium
Alklinity
Magnesium (not that important)
ORP (not that important)

 

[mojo]

sagent3000;122356 wrote:
Calcium
Alklinity
Magnesium (not that important)

Nope. These ions are really big (compared to hydrogen, used for pH), and while you can do spot measurements if you go through the calibration procedure every time, no controller can support these yet.

Technically speaking, that's not quite true. Any controller that can support an ORP probe can support an ISE (Ion Specific Electrode), which includes anything from ammonia to zinc. The problem isn't reading the probe- it's the long term use in an aquarium that's the issue...

 

[mwitten]

sagent3000;122356 wrote: is there a controller out there that will tell me all of the following

pH
Temp
Calcium
Alklinity
Magnesium (not that important)
ORP (not that important)

I think I can safely say no (but it would be nice!!) The only CA probes I am aware of are not that great, and have to be re-calibrated every time you use them (Pinpoint has one: OK as a toy, but not practical) I have not seen an Mg probe, and one that works in salt water in particular.

To a certain extent, you can infer Alk by looking at the pH trends over a day and other days... if the swing is getting pretty wide, your alk is getting low (it is a buffer, so it tends to reduce the pH swing).

pH, Temp, ORP and conductivity (to monitor salinity) are available on the Neptune AC3Pro and other brands, I believe (I have the Neptune).

-Mike

 

[mwitten]

mojo;122360 wrote:
Technically speaking, that's not quite true. Any controller that can support an ORP probe can support an ISE (Ion Specific Electrode), which includes anything from ammonia to zinc. The problem isn't reading the probe- it's the long term use in an aquarium that's the issue...

That, and sensitivity to interference from other things in the salt water, I think (may be wrong on that)?

-Mike

 

[mojo]

Right - it goes back to the ion selectivity. The probes work, on a basic level, by using a semi-permeable membrane, only allowing specifics ions to pass through the barrier and create a voltage potential, thus read in by the controller.

This becomes a problem when trying to make the probe selective to some ions and not others. For example, nitrate molecules are huge compared to hydrogen, sodium, and other basic ions in our tank. So making a nitrate probe is really difficult for use in our environment - it just can't sort between nitrate molecules and other molecules that may be smaller...

 

[cameron]

Sort of... http://www.vernier.com/probes/">http://www.vernier.com/probes/</a>

It isn't a controller but they can test for just about everything in a reef tank. Their new LabQuest looks very cool.

 

[mojo]

Sure- a lot of people sell the probes and the equipment, but it's the same issue - the probes can't be used for long in our tanks.

I spoke to both http://www.eidusa.com/">EID</a> and Aquarium Marine in depth about probes. Turns out, there's only 2-3 manufacturers of probes around the world- most are just rebranded.

So, even I or you can make an ISE controller - the issue is still the probes. Unless you're REALLY good at glass blowing....:lol2:

 

[cameron]

So what is the trick... you have to find a way to seperate out everything else then use a probe or some other system to mark and analyze? I did see a system that flushed a line with tank water, did some readings and then flushed in some RO/DI water. Never really understood why though.

Shame someone hasn't come up with a relatively inexpensive marking system with a color reader for a variety of tests.

 

[mojo]

I suppose if you could get everything else out of solution, then the probes would work fine.

What would work is a multi-function colorimeter that would add the reagent and test different things. Something like a combination of

 

[kwl1763]

Ya I agree a combo colorimeter could theoretically work but again then how do you sample and flush (where does the bad water go, how do you rinse with RO in between, etc.). None of these are constant monitoring and all require reagents! You would have to have a pretty sophisticated thing and do every so often tests no matter what. I would guess the system would run in the thousands!

 

[mwitten]

mojo;122416 wrote: I suppose if you could get everything else out of solution, then the probes would work fine.

What would work is a multi-function colorimeter that would add the reagent and test different things. Something like a combination of http://www.customaquatic.com/customaquatic/subsubcategorypage.asp?subcatindexid=di-cdm-spcm">these</a> , but the vial and reagents woudl be flushed between every measurement. Surely most of that electronics could be re-used....[/QUOTE]


Adding the reagents and indicators, mixing, timing, and you still have the problem with interference, I am afraid. Some (like Alk) are usually titration tests, though I have tried Unit Dose Vial types of tests for Alk and they do seem to work. I have the LaMotte SmartII, and while more accurate for some things, it does not save me any time. And you have to watch things like chlorides for some tests.

What we need is the AquaScum, of course...

-Mike