Digital SG / Salinity Meter vs. Refractometer

[usmcmarc]

It's me, the guy with neverending questions, again.

I picked up a TDS Digital SG / Salinity Meter for pretty cheap.

Of coarse now I'm 10x's more confused than ever.

I calibrated the meter (Wet method with a standard solution) and tested my SW. The digital meter says I'm at 1.022.

While my Refractometer gives me a reading of 1.023-1.024 (Yes, it's calibrated)

Which should I consider more accurate? I kinda like how easy the digital is, just dunk and read. While I always had difficulty discerning exactly where the line resting on the Refractometer.

Of coarse I also want to be sure I'm getting the most accurate reading as possible.

Opinions?

 

[roka64]

It probably depends on the degree of error of the equipment, kinda like the +/- of heaters (soory, I am not sure what the tech term is).

 

[Kurt_Nelson]

Seeing that you said you got the digital meter for "pretty cheap", I'd probably put my money on the refractometer! No way to really know unless you have a reference solution to test with.

While I don't have any experience with a digital meter for salinity, if it's like all the other digital meters it probably requires occasional recalibration to compensate for the normal drift. For that reason, I'm guessing that your refractometer might be the more consistent over the long haul.

Either way, whatever you choose to measure salinity with, stick with that method. A 0.001 difference won't really matter, but it's really consistency that you're striving for.

 

[usmcmarc]

When I said I got it cheap, I meant someone sold it to me for cheap...It's actually a very good meter (retail $130).

It came with three bottles of standard solution for calibrating. The one I used appears to have been already opened and used, cant guess how old.

So I opened a new bottle, and re-calibrated. Now the refractometer and digital meter are almost dead on. At most they are .0005 different.

**And on a separate note...Dumb question - MagFloat Algae Scraper, do you just leave it attached to the side of the tank, or is it supposed to be taken out when not in use?

 

[Kurt_Nelson]

I've seen folks do the algae scrapers both ways. Personally, I take mine out each time instead of "parking" it in the corner. I heard from someone that if you leave it in there, it can have a tendency to become an inadvertent algae collector itself.

I use mine every other day, and take it out when I'm done. I store it by "clamping" it between my shelf in my stand - fuzzy side goes on the top of the shelf, prickly side goes on the bottom of the shelf! Just make sure you don't get the two halves close to each other without something in between them - and NOT the tip of your finger.

 

[roka64]

I had a Marine algea magnet and left it in the tank, it rusted. I also noticed when I left it in the tank, it would collect those little filter feeding hard shell type critters. I clamp mine between two folded paper towels.

 

[MT79]

MagFloat Algae Scraper, do you just leave it attached to the side of the tank, or is it supposed to be taken out when not in use?

I would suggest taking it out if you have LR. Otherwise, as Roka said, small calcareous tube worms, AKA feather dusters, will grow on it and scratch the glass during use IME.

 

[roka64]

Mine grew on the sides and cut up my fingers. I had to scrape them off with a razor blade. Thanks, Mike, for the assist of the name of the "critters"!

 

[usmcmarc]

Thanks...It has been removed !