how to use sera GH tester???

[bslong]

how do u use sera GH tester???
i dropped one drop and the water turns brown....i'm expected to see red then brown then final result green.
but after dropping about 20 drops the water is still brown as in the first drop.
does it means that my water is more than 20dgh??? or less than 0dgh???

and how do u raise or drop the GH values????

[juggler]

It depends on whether you tank really has that high a gH. Mine at one time measured 17 dgH.
Or you can test with tap water. I think it is about 3 dgh? Not that sure.

Other things:
Did you shake the mixture after every drop?
The test kit is prone to turn bad rather quickly.

[vinz]

I hadabout 14 to 20 dGH in my tank at one point... I probably still do though I'm trying to fix that. I've tried using my kit to test lower GH (e.g. tap water) but the colour change is really hard to tell even in daylight near a bright window.

Never once has my kit started at anything close to red. It starts at brown for high GH water.

What you can try doing if you have some epsom salts (MgSO4) or calcium carbonate (or something that will raise GH by known amounts), to mix up a solution of known dGH and then test that. Singapore tap water shouldn't be higher then 6dGH, so if you raise 10dGH, your kit should read something by the 16th drop and no point testing beyond the 20th.

For reference,
1ppm Ca is approx 0.14dGH
1ppm Mg is approx 0.23dGH
Chuck Gadd's Dosage Calculator

[bclee]

When the kit started of brown colour, the kit is faulty. Probably oxidised or whatever.

It happened to my first GH kit. I bought a second one, it went from red to green... normal, colour change is distinct like the KH kit. But after a few months, it turned bad again.

(Vinz, in high GH water, it should appear very red.)

GH kit is known to go bad easily. I have hence given up on GH kits.

BC

[vinz]

[:0] That means I have never ever had a good GH kit!!! [:0]

[bclee]

To understand the GH test kit a bit more...

The GH test kit usually uses the EDTA titration method. Very briefly...

The Calgamite or Eriochrome Black T is used as indicators in EDTA titration. Both Calgamie and Eriochrome Black T are simialar. They form complexes with metal ions that appear wine-red in colour.

M++ + In- ---> MIn- (red)

M++: divalent metal ion (can be Ca++ or Mg++, etc.)
In: indicator
MIn: metal complex

EDTA is used in the tritration. The following reaction is involved.

EDTA + M++ --> M-EDTA + 2H+

When all the M++ in the water is depleted, the EDTA will react with the calgamite-metal complex.

EDTA + MIn-(red) --> MEDTA + In-(blue)

(The above explanation are simplified.)

BC

[geoffrey]

----------------
On 6/23/2003 1:01:44 PM

[:0] That means I have never ever had a good GH kit!!! [:0]
----------------

Looks like you are not alone!!

[Blue Whale]

[:] Heng ar...I learnt something new today.

Test at the Shop before bring home. kay kay...act blur act blur

[naturetan]

I'm not sure about Sera GH test kit. What I'm using is Aquarium Pharmaceuticals brand. Wonder whether it works the same?

I like this brand as its economical, testing is easy, keep adding the number of drops till solution turn from yellow to green. The drop amount corresponds to GH value, just like the KH test. Never face any vagueness with the result. Our tap water usually has 3GH, no doubt about that.

[bclee]

How much does the AP GH kit cost and where can I get it? Sounds like a good alternative for Sera GH kit.

Let me check out what type of titration method they use for this kit. But if you know you can share with us.

I believe Bioplast GH kits also uses the same method where the indicator goes from yellow to green. But they are quite expensive compared to Sera ones.

BC

[bclee]

I am suspecting that it is a acid-base type titration for the yellow to green test kit. OTOH, this type ot acid-base titration will be affected by the KH so it should not be.

Just curious... if you add a lot of baking soda into the tap water, does it affect the GH reading?

BC

[CoryDorus]

I thought is normal to turn brown then green for Sera GH
test kit. Is in the instruction too.

Tap Water in Central Hougang area is only 2-3dGH. I have never get 6 before yet. Tested on Sera and another Ger brand.
Taipei Tap water : 2-3 only.

One of my tank did went up to 17dGH. Suspect does "luohan" stone causing all the trouble.

[bclee]

Correct, it will go from red to brown to green.

The liquid in the bottle has to be red before you add to the water sample. If the GH is really very low, you may get brown at the first drop. IME with tap water or water with some GH, the first drop should be light red in colour.

BC

[naturetan]

BC,

I bought it at Clementi, Blk 328, can't really remember the shop name. It's located several shops from Clementi Flourist & Aquariums. This test kit cost $13.50, come with 2 bottles & test tubes for both KH and GH test.

Refer to this for product information.