Saltwater Aquarium Beginner's Guide | Episode 2: Rock & Sand

Before We Get Started

We know you came here for the Rock & Sand, but we have one side quest to tackle first. We're going to make some upgrades to the tank setup that are just easier to do now, before we add the heavy rock and sand.

The JBJ RF-45 Aquarium we're using comes with two AC return pumps, which are plug-and-play pumps that work for many reefers. There's nothing wrong with these pumps, but because Matthew values his aquariums being as quiet as possible, he's swapping them out for two of the AquaIllumination Axis 40. These pumps are not only quiet, but they're also fully controllable, which gives you the ability to fine-tune the return flow. 

Why You Should Consider the Axis Return Pumps

1. They're super quiet
2. They're fully controllable via the Mobius app
3. They easily integrate with other AquaIllumination and EcoTech products
4. The form factor makes them ideal for all-in-one rear filtration chambers

AquaIllumination Axis 20
(185 GPH Max Flow)

Ideal for all-in-one aquariums
up to about 15 gallons

AquaIllumination Axis 40
(400 GPH Max Flow)

Ideal for aquariums
up to about 40 gallons

AquaIllumination Axis 90
(925 GPH Max Flow)

Ideal for aquariums
up to about 90 gallons

Choosing Rock and Sand for Your First Saltwater Aquarium

When it comes to setting up your first saltwater tank, the rock and sand are way more important than most people realize. They are the foundation of your entire system. The right setup here means your tank will be more stable, your fish will feel at home, and you will have fewer headaches down the road. Aside from the aquarium itself, rock and sand are the most difficult to change out later if you regret your choices, so let's get it right the first time!

What Is “Live Rock”?

If you have ever wondered how a chunk of rock can be considered “alive,” you are not alone. In reefing, live rock is any rock (usually made of calcium carbonate) that gives beneficial bacteria a place to grow. These bacteria handle one of the most important jobs in your aquarium by turning toxic ammonia into safer forms that your tank can handle.

You will hear about two main types of live rock:

Wet Live Rock
Wet live rock typically refers to natural reef rock that has already spent time in saltwater, either in the ocean or in another established aquarium. It comes damp or fully submerged, loaded with beneficial bacteria and small organisms that help jump-start the tank's biological filtration. You can buy it from suppliers that harvest and ship it wet, or even get it from a fellow hobbyist who is breaking down a healthy tank.

Dry Rock
Dry rock is either human-made or quarried from ancient coral reefs that are now on land. It’s completely dry and sterile when you get it, which means it’s free from pests and unwanted hitchhikers. Once placed in your tank, bacteria and microfauna will naturally colonize it over time, turning it into “live” rock as your aquarium matures.

Which One Should You Pick?

For most beginners, dry live rock is the way to go. It is clean, pest-free, and lets you start with a blank slate. Wet live rock can work great too, but it often comes with hitchhikers and unwanted algae that new hobbyists are better off avoiding. With time, dry rock will come to life on its own as bacteria and microfauna move in.

CaribSea LifeRock

Aragonite-based rock with a natural coralline coloration

MarcoRocks

Our best-selling rock in traditional white or coralline color options

Real Reef

Calcium-based rock with a coralline-inspired coloration

Aquaforest

Lightweight and highly porus rock in a variety of shapes

Why Rock Matters

Reef rock does a lot more than just look nice. It gives beneficial bacteria a place to live, provides hiding spots for fish and invertebrates, and creates surfaces for corals and anemones to attach.

Think of your rockwork as the skeleton of your reef. It gives your tank its shape, but the real beauty comes later when corals, algae, and other life fill it in.

Aquascaping Tips

What is aquascaping? Aquascaping is basically designing how your rock will sit in the tank. It is part art, part puzzle, and part structural engineering.

A few things to keep in mind:

• Keep it simple. You don't need a mountain of rock. Leave room for corals to grow and fish to swim. Try not to build the structure more than half the height of the tank.
• Make it solid. Use a combo of super glue and epoxy (glue, epoxy, glue) so everything stays locked in place.
• Add caves and gaps. Fish love hiding spots and more habitat helps keep aggression down.
• Leave a cleaning gap. Keep a few inches of space between the rock and the glass so you can use your scraper later. This will also make the aquascape look less cramped and allow for coral growth in all directions.
• Plan ahead. Picture how your tank will look once the coral starts growing in.

A simple scape might feel a little bare at first, but once things grow in, you will be glad you kept it open.

Picking the Right Sand

Sand might seem like an afterthought, but it plays a big role in your reef’s health. It provides a vast amount of surface area for that beneficial bacteria we've been talking about. As a bonus, it makes a great spot for bottom dwellers like gobies and pistol shrimp.

Here is what to think about when choosing sand:

• Wet or Dry: Wet sand already has beneficial bacteria that can help your tank cycle faster.
• Color: White sand is the classic look. Black sand can look cool but can also be magnetic, which means it can scratch your glass when cleaning.
• Grain Size: Very fine sand can blow around, while coarse sand can trap waste. A medium grain is usually the sweet spot.

Popular Sand Options

Ocean Direct Sand

Live sand shipped in its own original ocean bacteria

Fiji Pink Sand

Popular sand option with small flecks of pink quartz mixed in

Special Grade Sand

Top-selling sand with a good middle-of-the-road grain size

Crushed Coral

A gravel-like substrate that's great for tanks with high flow

How Deep Should It Be?

For most tanks, one to two inches of sand works great. It is deep enough for bacteria to thrive and gives sand-dwelling creatures a comfy home. If you plan on keeping a pistol shrimp and goby pair, go closer to two inches so they have space to dig their burrow.

Tip: If you're not sure how much sand you need, use our handy Sand Bed Calculator.

Setting It All Up

When your rockwork looks good and feels solid, carefully move it into the tank before adding the sand. Putting the rock directly on the glass bottom keeps it from shifting down the road. This is especially important if you plan to add sand sifting fish or inverts.

When you add the sand:

• Do not rinse wet sand or you will wash away all the good bacteria you paid for.
• Spread it evenly or create a slight slope with more sand in the back for a more natural look.
• If you are not filling the tank right away, cover it with plastic wrap to keep the sand from drying out.

Leveling Your Tank

Now that the tank has some weight to it, it is a good time to make sure everything is level. Use a small level and check from side to side and front to back. If it needs adjustment, use composite shims under the cabinet’s feet instead of wooden ones. Composite shims will not swell or warp if they get wet, and they are easy to snap off once you are done leveling.

Once your rock and sand are in, you have built the base your reef will grow on. Your bacteria will have places to thrive, your fish will have places to hide, and your tank will already be starting to look like a real piece of the ocean.

Stay tuned for Episode 3!