Saltwater aquarium sand is used as the substrate (floor) of your tank.

deep sand bed benefits for saltwater aquariums

Saltwater aquarium sand is used as the substrate (floor) of your tank.

Freshwater aquariums commonly use pebbles as substrate (floor of the aquarium.)

Sand from a store for use in sandboxes should not be used in your saltwater aquarium, as it is not the same type of sand.

Some people prefer a deep sand bed, while other saltwater aquarium hobbyists prefer a shallow sand bed.

What is Live Sand in a saltwater aquarium

Live sand is natural reef coral sand that is collected live from the ocean or non-living coral sand that is cultured to make it live.

The millions of microscopic organisms living in the sand bed of your saltwater aquarium not only provide a food source to fish and all living things in your saltwater aquarium, but they help with the biological filtration of your saltwater aquarium.

Live sand means there are millions of micro organisms living the sand bed of your saltwater aquarium. There are many tiny crustaceans and micro and macro organisms that reside in the sand bed.

Live sand is comprised of microscopic biological bacteria that grows on it and inside the sand bed.

Biological filtration is the Nitrogen cycle. In other words, biological filtration is the necessary event of breaking down waste such as uneaten fish food and fish waste in your saltwater aquarium.

Live sand and live rock serve as the main base for biological filtration in a saltwater aquarium, while the organisms help consume organic matter in the sand bed. Organisms in your saltwater tank sand bed provide a natural food source for many aquarium inhabitants as well.

Live rock is the same as live sand, only in rock form. Over time, the rocks in your saltwater aquarium will be home to these millions of organisms, just like in your saltwater aquarium’s sand bed. These organisms live on both the inside and outside of all rocks in your saltwater aquarium.

Types of Live Sand to Use 

There are many types of sand (live or non live) to choose from, but the best is sand made from coral, such as coral sand, reef sand or sand harvested from the ocean floor.

It is NEVER recommended to use crushed coral in your sand bed. Crushed coral is made of larger bits and will trap uneaten fish food and fish waste. As this waste breaks down in your saltwater aquarium, you will see massive nitrate and phosphate problems, which are not good for anything living in your saltwater aquarium.

One of the best brands of sand to use for a saltwater aquarium is by Carib Sea. One of the most popular brands of sand for saltwater aquariums is Aragonite by CaribSea, which is what I use.

Live Sand vs. Non Live Sand 

  • Use 100 percent live sand, which can be costly but worth it.
  • Use a 50/50 combination of live sand (new store-bought live sand and non-living sand. By mixing the two together (called seeding) you save money, and the live sand converts the non-living portion of the sand into live sand over a period of time, as the biological bacteria and living organisms multiply and populate the non-living sand. Although this can save you money, it won’t be all that much. It is recommended to use all live sand.
  • All sand eventually becomes live sand over time, due to the nitrogen cycling process. However, starting from scratch requires more time to develop live sand. Using non live sand will not save you much money.
  • It is recommended to NEVER use live sand from another saltwater aquarium. Over time the sand bed in your saltwater aquarium will be filthy with sludge and toxins deep within the sand bed. Stirring this up can be fatal to your saltwater aquarium and its inhabitants. Always start with new live sand.

Deep Sand Bed vs Shallow Sand Bed 

A sand bed should be at least 1″ deep. How deep your sand bed is depends on you and what you like.

Anything under a 4″ deep sand bed is known as a shallow sand bed, while anything over 4″ deep is known as a deep sand bed.

Regardless of how deep your sand bed is, you should NEVER syphon / vacuum into the sand bed when doing a weekly water change on your saltwater aquarium!

Disturbing the sand bed with a syphon or any tool will disturb the delicate life in your sand bed and release toxins that should stay inside the sand bed!

Some people prefer a shallow sand bed, while others prefer a deep sand bed.

I have used both and prefer the deep sand bed for the looks of it, and for the powerful biological filtration a deep sand bed offers in a saltwater aquarium.

5″ deep sand bed in my 125 gallon saltwater aquarium. 200 lbs. of sand

The deeper the sand bed, the less oxygen there will be towards the bottom of the sand bed. Very important bacteria, called anaerobic bacteria, live deep in this oxygen-depleted area and help to remove nitrates from your saltwater aquarium.

Anaerobic bacteria are responsible for breaking down the uneaten food and fish waste and turning it into nitrogen gas, which escapes from the saltwater aquarium.

This is the power of a deep sand bed. Anaerobic bacteria is a powerful friend and needed in the nitrogen cycle of your saltwater aquarium. Anaerobic bacteria cannot live in shallow sand beds.

A sand bed in a saltwater aquarium of 5″ at least is a good start in housing anaerobic bacteria for proper biological filtration.

Some saltwater aquarium hobbyists have used no sand at all in their saltwater aquarium. I have tried this for the reason of ease of cleaning the saltwater tank. All loose food and fish waste is easily-syphoned out during a weekly water change since there is no sand to capture food or fish waste.

A deep sand bed is an excellent biological filter for saltwater aquariums.
A deep sand bed is an excellent biological filter in saltwater aquariums

I changed back to a deep sand bed of 5″ for my entire 125 gallon saltwater aquarium. I need the look of sand and wanted the powerful biological filtration a deeper sand bed offers.

Purchasing Live Sand for a saltwater aquarium

Live sand can be purchased online. I have included links above, to what many saltwater aquarium hobbyists use for their sand bed. Carib Sea remains a favorite brand for years.

The bag of live sand houses living creatures so make sure you only open the bag when you plan on adding the sand to your saltwater aquarium.

As with live rock, some die-off will take place during shipping, and the live sand will most likely go through a cycling process of some kind.

Die-off is the process of micro organisms dying within the sand during the packaging and shipping process.

Adding Live Sand to a saltwater aquarium

If you are using live rock in your saltwater aquarium, it’s best to put the rocks on the bottom of your aquarium and place the sand around it.

Placing rocks on top of the sand can result in the rocks falling as fish and burrowing creatures loosen the sand.

When adding live sand to your saltwater aquarium, it is best to submerge the entire bag of sand and cut it open carefully.

Once the bag of sand is cut open and completely submerged under water on the bottom of your saltwater aquarium, gently empty it out.

There will be a lot of cloudy water in your saltwater aquarium after adding sand and this subsides completely within a day.

Live Sand Maintenance 

The aquarium should include inhabitants that will stir or turn over the live sand. These animals are referred to as sand sifters, custodians or cleaners. Recommended types of detritivores (detritus is fish waste and uneaten food) include hermit crabs, shrimp, crab, sea urchins, sea cucumbers and starfish. Other great fish are gobies, mandarin fish, sand sifters or jaw fish. 

thin striped hermit crabs are a great cleanup crew for a saltwater aquarium sand bed
Thin striped hermit crab sifting through sand for food

It has been argued that star fish can be a hazard to your sand bed, as they sift a lot of the sand, destroying the micro organisms that live within said sand bed.

Always follow a good a maintenance routine when cleaning your sand bed. You should only siphon / vacuum any uneaten foods or excess debris from the “surface” of the sand bed and between rocks whenever needed. 

A turkey baster is a popular item to blow uneaten food and fish waste (detritus) from the rock in your saltwater aquarium. Make sure not to use the same Turkey baster on your Turkey!

It is suggested replace your sand bed with new live sand every 5 years to prevent die off (organisms dying in the sand bed.)

When replacing a sand bed with a new live sand bed, you will syphon out the old sand slowly, replacing your sand bed over the course of a month 1/4 of the sand bed at a time.

When removing an old sand bed, it needs to be done slowly so the toxins from the old sand bed are not released into your saltwater aquarium.

Always wear gloves when working in your saltwater aquarium!

Take your time and enjoy the saltwater aquarium hobby. Saltwater aquariums are part of nature and very delicate.

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