How to Use the Salifert KH/Alk Test Kit

I took out the Salifert test kit to check the KH/Alk in my 45 cm cube reef tank.

The kit is simple: a test vial, KH-Ind reagent, KH reagent, a 1 ml syringe, a plastic tip, and the instruction sheet.

The test itself is simple, but the details were much more confusing: where to line up the 1 ml syringe mark, and exactly where to count the color-change endpoint.

To summarize the test method:

1. Add 4 ml of tank water to the test vial.

Try to keep bubbles out as much as possible here.

2. Add 4 drops of KH-Ind reagent and gently swirl for 5 seconds.

3. Fill the syringe with 1 ml of KH reagent.

At this point, make sure the tip is tightly attached to the syringe.

The part that confused me most at first was drawing the KH reagent into the 1 ml syringe.

I thought the liquid itself had to come up to the 1 ml mark, but it should be aligned by the black rubber piston, not the liquid level.

If you pull more reagent to make the liquid surface line up with 1 ml,
you can end up using more reagent than the instruction sheet assumes, and the result can be thrown off.

Always line up 1 ml by the black piston, like in the photo on the right.

4. Add one drop, swirl for 2 seconds, and repeat until you reach the color-change point.

Another confusing point was exactly where to count the color change.

At first the solution looks blue or greenish; as you add the KH reagent one drop at a time, it gradually moves toward orange, pink, and red tones.

According to the instruction sheet, the endpoint is the first point where the color changes to an orange, red, or pink tone.

But there was a moment where the first visible change looked ambiguous, almost like 50% blue and 50% red.

At that point I was not sure whether to stop right away or add one more drop.

After looking it up, I decided that if the color still looks half-and-half, I would treat it as an intermediate stage and add one more drop.

Then, after swirling for about 1-2 seconds, I treat the first moment when orange, pink, or red is clearly dominant overall as the measurement point.

I do not wait until it becomes a deep red.

• Swirl well after every drop.
• View it against a white background.
• If blue/green is still the main color, add one more drop.
• Stop at the first point where red tones are dominant overall.

5. Read the syringe mark and check the KH/Alk value in the chart.

This Measurement

The KH/Alk reading this time came out around 9.6 dKH.

Since the black piston on the syringe was around the 0.38 mark, I just found that value in the chart and checked it.