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From the Aquarium Lab

30 Mesh (Grit) Substate

Evaluating ORP Values for an Anoxic Environment in 30 Mesh Sand Found in Hardware Stores

12 gallon lab tank with 30 mesh (grit) sand.

Published - 20240120, Revised:

The ORP values of 60 mesh (grit) sand were examined in the article “From the Aquarium Lab - Oxidation Reduction Potential of Substrate - Evaluating ORP Values of Substrate Size, Depth, and the Effect of Current,” published 2024.01.13. In that article, the ORP values at different depths were examined to find where the anoxic environment responsible for anaerobic denitrification begins.

In this article, 30 mesh (grit) sand ORP values were examined in this commonly available substrate found in the masonry section of the local hardware store. As with other substrates tested, 5 cm (2 inches) was placed on the bottom of a 12-gallon cube (14" x 14" x 14" [53 L, 35.5 x 35.5 x 35.5 cm]) aquarium on 2023.11.24. The sand was inoculated with beneficial bacteria with a small amount of 60 mesh sand that has been in a system for over a year.

30 Mesh (Grit) Sands
Images above of 30 mesh (grit) sands from the masonry sections of two different hardware stores.

When the 30 and 60 mesh sand is examined up close, it is clear the only difference is some 30 mesh gains are included, while the majority of the fine grains are also found in 60 mesh sand.

60 and 30 Mesh (Grit) Sands
For gain size comparison, Cemex 60 mesh (left) and Quikrete 30 grit (mesh) sand (right). 30 mesh sand allows the largest grains to be twice the size of the largest grains in 60 mesh. 30 mesh has the fine grains found in 60 mesh.

The “From the Aquarium Lab - Substrate Denitrification - Substrate Size Experiment” article concluded that 60 mesh sand aided in the denitrification of the system, while 10 mesh and 3 to 1 mesh (pea gravel) increased nitrate (NO3). Mesh or grit size indicates how many of the largest grains (end to end) it takes to equal 1 cm. Collecting ORP values of the substrate can show if anoxic environments could be detected in the three different grain (grit or mesh) size systems.


A 12-gallon cube (14" x 14" x 14" [53 L, 35.5 x 35.5 x 35.5 cm]) aquarium was set up and coupled to two other cubes to provide the same water chemistry and similar microbe biodiversity. The test aquarium was set up with 5 cm (2 inches) of 30 mesh (grit) sand.


Filtration for the coupled aquarium was a Sicce Shark Adv 400 - 600 internal power filter. Output from the internal filter was returned to the three coupled aquariums. A moderate current was supplied to the test system.

ORP Probes Installed 2024.01.05

For this experiment, ORP data was collected using a Milwaukee MC510 PRO Digital ORP Controller and three probes.

Milwaukee MC510 PRO Digital ORP Controller
Milwaukee MC510 PRO Digital ORP Controller.
Data Collected with Three Probes in 30 Mesh Sand

Probes were all moved to the 30 mesh sand to explore the depth of where the anoxic environment begins. Probes were maintained at the same depth for two days to allow the values to stabilize before collecting the final data values. Data was collected at .5 to 5 cm of depth:

Substrate Depth 3 Probes mV Value Average
.5 cm #1 = -207, #2 = -112, #3 = -56 -125
1 cm #1 = -434, #2 = -444, #3 = -453 -444
2 cm #1 = -433, #2 = -458, #3 = -433 -441
3 cm #1 = -418, #2 = -451, #3 = -441 -437
4 cm #1 = -427, #2 = -436, #3 = -437 -433
5 cm #1 = -411, #2 = -439, #3 = -437 -429
Summary of the Results

The ORP values collected from the three probes indicate that 30 mesh sand can provide a beneficial anoxic environment at a depth of less than 1 cm. The experiment shows beneficial anoxic environments in 30 mesh sand with moderate current can occur in less than .5 cm (1/4 inch). The hobbyist can use either 60 or 30 mesh sand in the aquarium to benefit from anaerobic processes in negative ORP mV value environments.

Contact Tony about this article.

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