Aquarium Gravel/Substrate; including pictures

Updated 5/3/10

QUESTION:
A friend is setting up a fresh water tank he has been given. It's tall
rather than long and fits in a corner unit. He's not sure weather to go
for sand or gravel at the bottom of the tank. What are the pro's and
cons? Is sand easy clean?


ANSWER:
I have used mixtures of gravels with success. The fine will settle to
the tank bottom while the course gravel will remain at the top.

For the average aquarium I recommend 2-3” of #3 gravel (#3 gravel is .2 to .5 cm in size) or a larger pea sized gravel (#5). This tends allow for less build up of hydrogen sulfide producing anaerobic bacteria than with sand. The down side to larger gravel is that it will allow for more waste particle or eaten food to accumulate in the larger crevices that will form between the pebbles. With proper cleaning procedures though, waste accumulation should not be a major problem.

If you are not planning to add plants, I would be careful with the use of #00 or #1 sand (#1 sand is commonly used in mortar/masonry) as this can cause dangerous anaerobic Hydrogen Sulfide production in un-planted tanks when anaerobic de-nitrification goes from production of nitrogen to hydrogen sulfides do to sulfur reduction; please see this article for more on this subject:
Hydrogen Sulfide production in anaerobic De-Nitrification for Aquarium/Pond Nitrate Removal

If #1 sand is used in a non-live planted freshwater aquarium, the use of #3 or #5 provides a way to lower your chances of hydrogen sulfide product and tends to trap larger debris/organic mulm for easier cleaning with a gravel vacuum, Cleaning Machine, or Eheim Sludge Remover.

Sand is good for heavily planted aquariums, as it provides a better anchor for the roots and even more important sand traps nutrients and symbiotic bacteria needed by plant roots. If used for live plants, I recommend about ½” #00 or #1 sand followed by 2-1/2” of medium (#3) gravel, with laterite mixed in around plant roots. Be careful when vacuuming sand though, as it is easy to suck it into the vacuum and if it is a powered vacuum, this can damage it or clog a Python or similar. I recommend quick probes into sand and possibly ‘kinking’ the tubing behind the vacuum nozzle to allow the sand to settle back into the tank.

If your aquarium is going to be only lightly or moderately planted, I recommend sand only in the area around the plant roots and use #3 size gravel (or larger) elsewhere.
Sometimes in these lightly planted aquariums I will actually substitute sand for lightly sifted sandy soil. I prepare this by digging in a clean area for my soil then I rinse it gently (as if I am panning for gold). After I have rinsed out the muck and dirt I had a 20/1 water/bleach solution for a few minutes then rinse it with a De-Chlorinator and I am ready to go.
A better yet method (that can be use to totally replace the aquarium substrate or used only around plant roots) are products such as Eco-Complete or Azoo Plant Grower Bed . Azoo Plant Grower Bed in particular will add iron, calcium, magnesium, potassium, sulfur plus and many other elements to nourish your aquatic plants. An added bonus with Azoo Plant Grower Bed is it will stabilize pH while maintaining a lower pH value without the use of CO2. Excellent when combined with Sea Chem Excel

Here are a few pictures of Aquarium Gravels I have used and recommend:
(Please click pictures to enlarge)

Regular Pebbles; excellent pea sized (slightly larger than pea size) for use with Goldfish and Bettas





Coral Sea Pebbles; another good choice for Goldfish, Bettas and other larger pea sized gravel applications





#3 Aquarium Gravel, natural rainbow; excellent overall aquarium gravel for most freshwater applications




#3 Aquarium Gravel, White Coral; excellent overall aquarium gravel for most freshwater applications (this is NOT actual coral, rather natural rocks with the color of coral rock)


I would recommend checking with local decorative rock/building supply business for these substrates, such as this Sun Burst Rock in Los Angeles County.


Also consider the fish you plan to have;

*Goldfish tend to root around and can get the #3 gravel stuck in their mouth, so for them, a #1 sand or larger #5 pebble would be better (or even no gravel at all!). See the above pictures for some ideas.

*Cory Catfish should be kept in an aquarium with sand or rounded gravel so as to not damage their barbells.

*African Cichlids and other digging cichlids do best with a #3 gravel (or a #3 crushed coral can be used for African cichlids).

*Large predators such as Arowanas that may on occasion try and capture prey on the bottom by swooping down unto the bottom often do best with a coarse rounded gravel so as to prevent injury or even no gravel at all.

*For hospital, breeding, or heavily populated temporary holding tanks; no sand or gravel is best. This allows for less waste build up, less possibility of waste matter or substrate absorbing medication in a hospital tank, and less rotting organic sludge in a holding tank.
A bare tank is easier to vacuum debris and allows no chance of fry being caught in the substrate.


Consider mixing different types of natural or colored gravels to achieve a look you like. I think blue mixes very well and can bring out certain fish colors. Black gravel or pebbles also mixes well, especially with natural gravels.

For hospital, breeding, or heavily populated temporary holding tanks; no sand or gravel is best. This allows for less waste build up, less possibility of waste matter or substrate absorbing medication in a hospital tank, and less rotting organic sludge in a holding tank.


By Carl Strohmeyer
American Aquarium Products-Aquarium Information