Brown Diatom Algae Control
March 30, 2010 – 5:48 am | No Comment

What are Brown distom algae? Why do they grow in our aquarium and how to get rid of them. In this post you will find valuable information about this algae and how to control them.

Read the full story »
Saltwater Basis

So you want to start a saltwater aquarium? Well this section is for you.

Fishkeeping basis

So you want to start a freshwater aquarium? Well this section is for you.

Planted tank basis

So you want to start a planted aquarium? Well this section is for you.

Featured Websites

Learn more about some of the greatest aquarium websites around.

Algae Control

Algae overgrowth? Find here all you need to know to get rid of them!

Home » Fertilizers and CO2, Planted tank basis

pH Drop Checker And How To Use It

Submitted by on April 25, 2009 – 5:59 pm6 Comments

It’s not easy to write up about Drop Checkers in a short answer so I decided make this post and use as many examples and images as possible. By the end of this article, you should know what a Drop Checker is and how to use it.

So a drop checker looks like this:

drop checker

What is this thing?

As describe in a previous post, a Drop Checker is a U shaped glass container filled with a 4 KH solution and a pH indicator. The reservoir is build so that there is an opening that allows gas (CO2) exchange between the solution and the water in the aquarium. As the CO2 gasses off from the aquarium into the drop checker, the pH lowers and the color changes. By looking at the color in the reservoir, we can easily find how much CO2 there is in the aquarium.

How to use a Drop Checker?

1. The first step is to make a 4 KH solution. To make this solution, we mix distilled water with sodium bicarbonate (baking soda) until we achieve 4 KH. It does not take much to get 4 KH. Because it can be difficult to work with small quantities, we are going to make a 40 KH solution. Then, all you need is to mix that solution with more water to make it 4 KH.

0.99 gram of baking soda in 1 liter of distilled water = 40 KH

To dilute the solution and make a 4 KH solution, take a 10ml sample of the 40KH reference and add it to a 90mls of distilled water.

drop checker

Tips`: You can also use sodium carbonate instead of sodium bicarbonate. To make sodium carbonate, you need to cook the baking soda for 30-45 min at 400F before weighing to remove water and CO2 in the baking soda. This will make your solution even more accurate

2. Turn the drop checker upside down and fill it with your 4 KH solution and add 3 drops of bromothymol blue (Blue liquid which can be found in low range ph test kits). Filling a Drop Checker can take a little practice. Tilt the checker slightly so the solution runs into the ball. Try to fill the ball half full, as this ensures the maximum surface area for gaseous exchange.

drop checker

drop checker

drop checker

3. Turn the Drop Checker back over, and insert into the aquarium, making sure there is an air gap. At this point, the solution in the checker should be blue.

drop checker

How do we read it?

Once the checker is in the aquarium, it will take a few hours before CO2 in the aquariums exchanges across the air gap. After 2-3 hours, CO2 in the checker and CO2 in the aquarium should be the same.
The increased CO2 level in the Drop Checker will affect the pH which will change the color of the regent.

A blue colour indicates you have a CO2 level of 25ppm or less
A green colour indicates your have a CO2 level of 26 – 35ppm
A yellow colour indicates you have a CO2 level of 36ppm or more

Why is it accurate?

To measure CO2 in water, we need to have an accurate measurement of pH and KH.
Since we know we are working with 4 KH, we don’t need to measure KH which reduce risk of error.
We also know that there are no other buffer that could influence our reading which reduce risk of error again.
The color of the solution only turns green when the optimal concentration of CO2 is achieved in the aquarium water.

Feel free to use the comment box bellow if you have any question about Drop Checkers and how to use them

Article written by Patrice Lapointe for

pH Drop Checker And How To Use It 5.051

Popularity: 11% [?]

Related Posts

  1. How to measure co2 in a planted tank
  2. Calculating fertilizer solutions for the planted tank
  3. Co2 in Planted Aquarium
  4. Aquarium Fertilizer Calculator
  5. How much CO2 in planted aquarium?


Leave a comment!

Add your comment below, or trackback from your own site. You can also subscribe to these comments via RSS.

Be nice. Keep it clean. Stay on topic. No spam.

You can use these tags:
<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>

This is a Gravatar-enabled weblog. To get your own globally-recognized-avatar, please register at Gravatar.