Your First Reef Tank: Everything You Need to Know

Starting a reef tank can feel intimidating and overwhelming. At first, it feels like there is so much to think about: water chemistry, corals, lighting, and filtration. Reef-keeping can be one of the most rewarding experiences in the world once you develop the right foundation. Our goal at PNW Custom is to make taking that first step a little easier.

Let's go over the essential information to help you start your journey into the saltwater world.

1. What is a Reef Tank?

Our oceans are incredibly sophisticated and nutrient-rich environments: teeming with life, balanced chemistry, and constant motion. They maintain clean, well-circulated saltwater, consistent temperature, and stable lighting that fuels coral growth and supports countless marine species.

A reef tank is essentially a small-scale version of this ecosystem. It recreates the natural processes of the ocean within aquarium walls, allowing you to sustain coral reefs, fish, and invertebrates in your home. Through intentional balance of water chemistry, temperature, and flow, your reef becomes a living, breathing ecosystem where every organism plays a role.

2. Water, Rock, and Sand

Systems like the 5-Gallon Small-In-One XL and other PNW Custom tanks come with everything you need to begin your reef-keeping journey: filtration, lighting, lids, and return pump, leaving only water, rock, and sand for you to add.

• Saltwater: Use a high-quality reef salt mix and RO/DI water for purity. To get started, we recommend purchasing your water pre-mixed at your local aquarium store. This ensures that you are getting properly balanced water to start, and it takes another step out of the equation which makes your life easier. You can always learn how to make your own saltwater at home at a later point, once you establish confidence in your maintenance routine.

• Rock: Live or dry rock serves as the biological backbone of your aquarium, providing surface area for beneficial bacteria. We recommend starting with live rock. Live rock benefits a reef tank by providing natural biological filtration through beneficial bacteria, serving as a foundation for aquascaping and coral growth, and increasing biodiversity with micro-organisms.

• Sand: Adds natural beauty and helps stabilize your rock structure. We recommend starting with live sand. Live sand offers the same benefits of live rock and also helps speed up the tank cycling process.

Tip: Like water, you can often find both live rock and live sand at your local aquarium store. For our 40oz Micro Tank and 1 Gallon Small-In-One, we offer pre-portioned live sand and live rock ready to purchase.

3. What Is the Cycling Process?

Before adding fish or corals, your tank needs to establish a biological filter: a process known as cycling. This step allows beneficial bacteria to grow within your rock, sand, and filtration media, forming the natural system that breaks down waste and keeps your water safe.

Here’s how it works: when organic matter like fish waste or leftover food breaks down, it releases ammonia, which is toxic to marine life. Beneficial bacteria convert ammonia into nitrite, and then into nitrate, which is far less harmful and can be removed through water changes or absorbed by corals and algae.

The cycling process typically takes around 3–6 weeks, depending on your setup and materials. However, you can speed up this process by using live rock and live sand instead of dry versions. These come pre-colonized with beneficial bacteria and microorganisms that jump-start the nitrogen cycle, helping your tank stabilize faster and safely.

4. The Basics of Reef Tank Filtration

Your filtration system is what helps keep your reef tank clean and healthy.

Most setups use three types of filtration:

• Mechanical: Removes debris like uneaten food and detritus using a sponge or filter floss.

• Chemical: Uses carbon to clear water and remove impurities.

• Biological: The heart of every reef tank. Beneficial bacteria living in live rock, live sand, and ceramic media break down waste into safer compounds.

Tip: PNW Custom tanks already come with a multi-stage media basket, making it simple to set up all three types of filtration in one compact space. Want to upgrade your filtration system even further? Our new Filter Rollers are designed to make maintenance a breeze and removes the need for regular filter pad changes.

5. Maintenance and Stability

Consistency is key in reef keeping. Following a regular maintenance routine helps prevent sudden changes in water quality, which can stress or harm your livestock. Even small, consistent tasks make a huge difference in keeping your system healthy and stable over time.

A few common tasks include:

• Water Changes: Replace about 15–25% of the water volume each week to replenish trace elements and export waste.

• Check Salinity: The ideal salinity for a reef tank is between 1.024–1.026 specific gravity, which closely matches natural seawater. We recommend using a Hanna salinity tester.

• Top off with Freshwater (RODI): Saltwater tanks must be topped off with RODI freshwater to counteract evaporation, which removes only water and leaves the salt behind. An Auto-Top Off is a great tool that monitors the water volume and tops off the water for you automatically.

• Clean Filter Sponge/Pad: This is important mechanical filtration that requires cleaning to remove solid waste and organic matter that would otherwise break down in your tank.

Tip: At PNW Custom, we know how important it is to stay organized, especially for new reefers. That’s why we offer free downloadable Weekly Maintenance Checklists on our website. These printable sheets make it easy to track your water changes, cleaning schedule, and testing results so you can build good habits and keep your reef thriving for years to come.

6. Choosing the Right Tank Size

For beginners, small desktop aquariums are perfect for learning the basics without overwhelming upkeep. PNW Custom’s Small-In-One XL (5-Gallon) and Mini Pond (4-Gallon) are ideal for compact spaces like desks, countertops, or nightstands, while still offering the essentials of a full reef setup.

These tanks include:

• Built-in filtration compartments for mechanical, chemical, and biological media

• An adjustable return pump for circulation

• An LED light designed for coral growth

• A self-leveling mat for stability

• Polycarbonate lids to reduce evaporation

These features eliminate the guesswork of equipment compatibility, allowing you to focus on creating your dream reef.

7. Choosing the Right Livestock

Once your tank is cycled and stable, it’s time for the most exciting part: choosing your reef’s inhabitants! Selecting the right combination of fish, corals, and invertebrates is essential for long-term success.

Start simple with beginner-friendly fish and invertebrates that are hardy and adaptable to small systems. Popular starter choices include clownfish, gobies, hermit crabs, snails, and soft corals like zoanthids and mushrooms. These animals are resilient, colorful, and great teachers for learning the rhythms of reef care.

Before adding anything new, it’s important to research compatibility to ensure your livestock will coexist peacefully and thrive in your specific tank size and setup. To make this process easy, PNW Custom offers free downloadable compatibility charts for both invertebrates and fish. These printable guides help you plan your aquarium community confidently, ensuring you choose suitable species for your particular PNW Custom tank.

Final Thoughts

Caring for a reef tank is a journey of discovery. You’ll learn about biology, chemistry, and design, but most importantly, you’ll create a living piece of the ocean that brings relaxation and inspiration to your space.

Whether you start with a 1 Gallon Small-In-One, a 5 Gallon Small-In-One XL, or our 4 Gallon Mini Pond, you’ll have everything you need to begin your reef-keeping adventure. Explore our full collection and start your own reef today.

Want to learn more? We offer a variety of educational how-to videos on our YouTube channel to help you get started: