Marine/Reef Aquarium Sand: Deep Sand Bed or Shallow? Coarse or Fine Grain Sand? Find Out!

Today we are going to answer some of the most frequently asked questions about choosing sand for a saltwater aquarium. Read on to discover what kind of sand is best for your tank plus get the truth about how deep your sand bed should really be.

We offer a wide variety of sands and each type has its advantages and disadvantage. Similarly, a shallow sand bed also has advantages and disadvantages over deep sand beds. To help decide what you need, you first need to decide what you want to achieve!

A shallow sand bed measuring 1.5" to 2" deep with a fine grade sand is great for those of you who like a natural looking, brilliant sand bed. The CaribSea Fiji Pink and Aragamax are the two most popular fine grade sands. The fine particle size is great for filtration because there is tons of surface area for bacteria to grow on. Furthermore a shallow bed is easy to keep clean and will not clog up with detritus. The drawback is that because the sand is fine and lightweight, it gets blown around easily in reef aquariums with high water movement and you can end up with bare spots on the bottom of the tank.

Using a deep sand bed with fine grain sand is great because of the increased biological filtration. It will promote both aerobic and anaerobic bacteria helping to break down waste and remove nitrates. A deep sand bed is typically 6" to 8" deep. Within the first 2" to 3", aerobic bacteria will thrive and help breakdown waste and produce nitrates. As you go deeper into the sand bad, the water will be less oxygenated and therefore anaerobic bacteria will thrive. This type of bacteria is very efficient at denitrification which will turn nitrate into nitrogen gas.

The drawback to a DSB is that you need much more sand and it takes up a significant portion of your aquarium. Additionally, there is also the potential for pockets of poisonous hydrogen sulfide to develop if there is not enough organisms to keep the sand bed stirred and clean. Allowing a deep sand bed to become stagnant and full of detritus will eventually cause a big problem in your tank so be sure to maintain a solid clean-up crew with animals such as nassarius snails, sand sifting gobies and starfish, sea cucumbers, conchs and even hermit crabs.

A shallow sand bed with coarse sand is what many of us here at MD prefer to use. CaribSea Special-Grade sand is perfect for this type of sand bed and is one of our most economical and best-selling substrates. With coarser sand, you will have less surface area for bacteria to grow on and a higher chance of detritus getting trapped in the sand. However, the advantages are that because it is heavier, it does not get blown around easily and you are less likely to have bare spots at the bottom of your aquarium. Coarser grain sand can also be cleaned with a gravel vacuum during water changes so it is easy to keep clean and free of detritus.

We advise against using a deep sand bed with coarse sand. A coarse grain sand bed that is more than 2" to 3" inches deep is a dangerous combination because it will quickly become clogged with detritus and increase the nitrate in your tank. You will also have a much greater chance of getting toxic pockets of harmful gas and it is difficult to keep clean, even with a hefty clean-up crew.

Once you have decided on the type of sand bed you want, you will have some options when it comes the appearance and color of the sand. CaribSea Aragamax and Oolite sand have sort of become the standard for fine grade sand. Both are fine, beige-colored sands that are uniform in color and size.

The CaribSea Fiji Pink and Bimini are also beige colored, fine grade sand with small bits of pink mixed in which gives it a very unique and natural look.

If you want to step outside the box a bit and are looking for something different, the CaribSea Tahitian Moon or Indo Pacific Black sandare formed from volcanic ash in Hawaii. The black sand gives an amazing contrast to your fish and corals, but can be tough to keep clean.

For coarse grade sand, the CaribSea Special-Grade sand is the one to look for and is available both live and dry.

How many pounds of sand you need will vary based on the particular sand you choose. We have a handy Sand Bed Calculator on our website that allows you to enter your tank size along with the grain size of the sand to estimate of how much sand you will need.

With so many choices and the dramatic way sand can transform the appearance of an aquarium, you now see how this is really a worthwhile topic to consider while planning your aquarium build.

If you need help choosing the right sand or would like to place an order, please contact our aquarium experts for fast and friendly service. If you found this blog post and the accompanying video helpful, please like, share and subscribe to show your support and help out other hobbyists!

Until next time... take care and happy reef keeping.