The old adage that you can put one inch of fish per one gallon, five gallons, or even ten gallons of saltwater just doesn’t make sense anymore. Determining how many fish can you put in a saltwater aquarium requires a nuanced understanding of three key factors:
- the fish itself,
- the habitat,
- and the filtration system.
In this blog, we will delve into these factors and provide definitive stocking recommendations for five different tank sizes, from a compact 15-gallon setup to a spacious 150-gallon tank.
Key Considerations
1. The Fish
First and foremost, it is crucial to consider the specific characteristics of the fish you intend to keep. Each species has unique requirements and behaviors that can significantly impact the stocking capacity of your tank. Key aspects to consider include:
- Size: How large will the fish be when fully grown? A juvenile fish might seem small now, but it could quickly outgrow your tank.
- Diet: What do they eat, and how often? Some fish have specific dietary needs or feeding frequencies that can affect the tank’s nutrient load.
- Temperament: Are they peaceful, aggressive, or somewhere in between? Compatibility with other tank inhabitants is essential to prevent stress and conflict.
- Habitat Preference: Where in the tank do they prefer to live? Some fish occupy the bottom, others the middle, and some the top, so a diverse tank can support more fish if their territories don’t overlap.
Check out our Beginner Guide For Saltwater Fish Here.
2. The Habitat
Next, consider the physical environment inside your tank. The layout and composition of your tank can greatly influence how many fish it can support. Important factors include:
- Tank Dimensions: Is it a tall tank or a short and long one? Horizontal space often matters more than vertical space when it comes to stocking.
- Substrate: Is there a sandbed, and if so, how deep is it? Some fish, like gobies, need sand to sift through, while others prefer rocky landscapes.
- Decorations: Are there simple plastic decorations or elaborate rock structures with caves for hiding? Complex environments with plenty of hiding spots can reduce stress and aggression among fish, allowing for a higher stocking density.
3. The Filtration
Lastly, the efficiency and capacity of your filtration system are critical. Good filtration can handle the bioload of more fish, keeping the water clean and parameters stable. Consider the following:
- Current Filtration: How much filtration does your tank currently have? This includes mechanical, chemical, and biological filtration.
- Potential Upgrades: How much more filtration are you willing and able to add? Options include fleece rollers, protein skimmers, macroalgae refugiums, turf algae scrubbers, and automatic water change systems. Enhanced filtration can mean the difference between a lightly stocked tank and a vibrant, bustling community.
Explore all of our Gear Guides Here.
Recommendations Based On Tank Size
Our first example is the 15-gallon HelloReef all-in-one kit. This compact setup comes with a rear filtration chamber equipped with a filter sock, sponge, and ceramic media. Inside the display portion, the habitat consists of a reef rock structure and a 1.5-inch sandbed. Assuming a semi-weekly filter sock change and a 20-30% weekly water change, this tank can comfortably house a few small fish.
How many fish can you put in a saltwater aquarium that’s 15 gallons?
- Number of Fish: 3
- Suggested Stock List:
- A small pair of Ocellaris Clownfish
- A Yasha Goby and Pistol Shrimp combo
Despite its small size, this 15-gallon habitat can also be filled with various invertebrates such as corals, anemones, sea urchins, snails, and hermit crabs to create a lively and engaging ecosystem.
Next, we have the 25-gallon all-in-one lagoon from Innovative Marine. This tank’s design provides significantly more horizontal space compared to the 15-gallon cube.
Its rear filtration chamber includes a filter sock and fiber filter balls, with enough room to add a protein skimmer or a hang-on-back refugium if needed. The display portion features a 1-inch deep sandbed and plenty of rock work to offer hiding places for the fish.Â
How many fish can you put in a saltwater aquarium of this size?Â
- Number of Fish: 10
- Suggested Stock List:
- A pair of Ocellaris Clownfish
- 5x schooling Masked Gobies
- A Banggai or Pajama Cardinalfish
- A Yasha Goby with Pistol Shrimp
- A Six Line Wrasse
This mix includes smaller fish that inhabit different areas of the tank, helping them coexist peacefully. Additionally, as with all the tanks discussed, this setup can be enhanced with a variety of invertebrates like anemones, corals, and other cool creatures to create a dynamic and visually appealing aquarium.
Our third tank is the 48-gallon lagoon style from Maxspect. At 3 feet long and 20 inches wide, its dimensions are similar to a standard 40-gallon breeder setup but with enhanced filtration capabilities.
This tank includes a sump with filter socks and a protein skimmer, leaving plenty of room for additional filtration methods like a turf algae scrubber or a macroalgae refugium. With a 2-inch deep sandbed and a large rock structure full of nooks and crannies, this tank provides an ideal habitat for a variety of fish.
How many fish can you put in a saltwater aquarium of this size? Here’s the recommendation:
- Number of Fish: 17
- Suggested Stock List:
- 2x Ocellaris Clownfish
- 2x Pajama Cardinalfish
- One Sand Sifting Goby
- One Firefish
- One Fairy Wrasse
- 6x Masked Gobies
- One Algae-Eating Blenny
- One Aiptasia-Eating Filefish
- One Longnose Hawkfish
This is a relatively heavy stocking list, but the robust filtration system can handle the bioload. Keep in mind that hawkfish might prey on shrimp, and filefish can occasionally nip at corals, so monitor their behavior closely.
Our fourth example is an 82-gallon aquarium with a sump from AquaForest. This tank has a similar footprint to the 48-gallon lagoon but offers additional water volume due to its greater height. The filtration system is almost identical, with filter socks, a protein skimmer, and ample space for further upgrades.
How many fish can you put in a saltwater aquarium of this size?
- Number of Fish: 23
- Suggested Stock List:
- 2x Clownfish
- 3x Pajama Cardinalfish
- One Sand Sifting Goby
- One Firefish
- One Fairy Wrasse
- 10x Masked Gobies
- One Algae-Eating Blenny
- One Aiptasia-Eating Filefish
- One Longnose Hawkfish
- 2x Clown Gobies
This setup allows for a slightly higher stocking density, but the key is to choose small, peaceful fish that can coexist without causing stress or conflict.
Finally, we have the 150-gallon peninsula style tank from Red Sea. With 150 gallons in the display plus an additional 36 gallons in the sump, this large system can accommodate a substantial number of fish.
Filtration is maximized with a fleece roller mat, a protein skimmer, and either a macroalgae refugium or a turf algae scrubber. Measuring 5 feet long and over 2 feet wide, this tank has a large footprint that is perfect for larger fish such as tangs and angelfish, though we need to balance the number o…
How many fish can you put in a saltwater aquarium of this size?
- Number of Fish: 52
- Suggested Stock List:
- 3x Tangs
- 5x Anthias
- 2x Clownfish
- One Rabbitfish
- 6x Chromis
- One Coral Beauty Angelfish
- 2x Sand Sifting Gobies
- 2x Algae-Eating Blennies
- 2x Mandarin Dragonets
- One Midas Blenny
- 15x Schooling Masked Gobies
- One Copperband Butterflyfish
- 2x Firefish
- 2x Shrimp Gobies
- 2x Hawkfish
- 5x Cardinalfish
This extensive stocking list features a mix of small and large fish, all chosen for their compatibility and unique roles within the tank ecosystem.
Conclusion
Choosing the right fish, understanding your tank’s habitat, and optimizing filtration are key to maintaining a healthy and vibrant saltwater aquarium. By carefully considering the size, diet, temperament, and habitat preferences of your fish, as well as the dimensions and filtration capabilities of your tank, you can create a thriving aquatic environment.
How many fish can you put in a saltwater aquarium ultimately depends on these factors, but with the right approach, you can enjoy a beautiful and thriving ecosystem
Check out the video for this blog below, and until next time… Be Well & Happy Reefing Everybody! 🙂
