From exotic dragon gobies to unusual puffer fish, there are many beautiful aquatic companions that thrive in brackish water, a mix of fresh water and salt water. While these fish require more maintenance than many types of standard pet fish, brackish water species are more diverse and spectacular. However, a lot can go wrong if you add brackish fish to freshwater or saltwater aquariums. To avoid this common mistake, our guide explores five pet fish that need brackish water. Discover simple care tips for each species and why they make wonderful additions to any aquarium.
1. Mollies: A Common Livebearer Fish
The molly is a livebearer and one of the most underrated brackish water fish. They’re popular in freshwater tanks, but mollies are versatile fish that thrive in both freshwater and brackish water environments (provided it is fairly alkaline). Various mollies, including sailfin mollies, black lyretail mollies, gold dust mollies, and marble lyretail mollies, are striking additions to brighten an aquarium.
Caring for mollies is easy. They require water parameters with a pH of between 7.5 and 8 and a temperature of 78℉ and 82℉. They are sensitive to ammonia, so be sure to keep the tank clean with frequent water changes and a strong filtration system.
Interestingly, some marine fish keepers have used mollies in full salt water to consume algae and cycle their tanks. If you have freshwater mollies, don’t just place them into saline water. Gradually increase the salinity to help them adjust to brackish conditions. Better yet, purchase mollies that are raised in brackish water making it easier for them to transition to the new conditions. Adding a molly that once thrived in a freshwater aquarium could go into shock if it’s immediately placed in a brackish water tank.
2. Puffer Fish: Fascinating But Aggressive Once Mature
Puffer fish are curious creatures and a great addition to brackish aquariums because they’re interactive fish that enjoy mental stimulation. The green spotted puffer is the best for brackish water, and despite being sold for freshwater aquariums, these aquatic creatures need some marine salt to thrive. The green spotted puffer reaches six inches in length, but they’re fairly aggressive once they reach maturity. To avoid ongoing aggression, only house one green puffer (or several) in a large tank, but never keep them with smaller puffers. Immaculate tank conditions are necessary for these fish because they’re extremely sensitive to ammonia and nitrites. If you notice that the underbelly of your puffer is off-white, it could be a sign of parasites or issues with water salinity.
Another interesting puffer for the brackish aquarium is the figure-8 puffer. Growing to around three inches, they come from Southeast Asia’s freshwater regions, but a fair number of keepers raise them in brackish water. They are one of the smallest puffers and do well in a setup where salinity is increased by 0.002 weekly when replacing tank water.
3. Columbian Shark: Not Recommended for Beginners
If you are looking for an impressive-looking fish, the Columbian shark is the ideal brackish water pet. These active fish reach a whopping 20 inches! Yet, they’re not recommended for beginners. Also known as Columbian cats, these streamlined fish need a 75-gallon tank to accommodate their size and provide enough room to swim. They cannot be kept with smaller fish such as mollies or guppies as these tiny fish will become lunch!
To make a Columbian shark fish feel secure, add rocks and driftwood to the tank. They prefer open spaces to move around but should have a hiding spot or two. Add a sandy substrate where they can peacefully explore the bottom of the tank. Columbian sharks tolerate temperatures up to 82℉ and require a slightly acidic pH of 6.5 to 7.5. A Columbian shark will live up to 15 years under the right conditions. Should you decide to add one of these magnificent fish to your aquarium, be prepared for long-term companionship.
4. Gobies Are Peaceful Fish
Gobies are unusual fish, but they’re excellent additions to brackish water aquariums. From tiny bumblebee gobies to the longer dragon gobies, these brackish water fish are fun to watch and easy to maintain.
The dragon goby is commonly called the violet goby because of its blue to purple sheen. The bottom dwellers have elongated and almost eel-like bodies they use to glide over the aquarium floor picking up leftover food. You’ll notice the very large mouth on this species; however, they’re quite peaceful and get along with tank mates such as archerfish, swordtails, and bumblebee gobies. The violet goby needs a 30-gallon tank and excellent water conditions to prevent ammonia poisoning.
The bumblebee goby is a yellow and black striped fish growing only to one inch. Two of these gobies can be placed in a 10-gallon tank, but some hobbyists recommend housing larger groups of six to eight gobies. Because of their incredibly tiny size, stick to small tank mates like mollies and glass fish. These little gobies prefer a pH of 7 to 8.5 and will handle water temperatures of up to 85℉.
5. Archerfish: Social Creatures with Unique Adaptations
The term “archerfish” refers to a group of brackish water fish that have gained attention as colorful aquatic pets. These fish have a unique ability in the wild to squirt water and “shoot” prey off of branches and plants. Once the insects land in the water, they’re snatched in seconds. Pet archerfish for the brackish aquarium grow up to 10 inches, and because they’re social fish, they should be kept in groups. The spitting fish make fairly good pets with a lifespan of 10 years, making them a sizable commitment.
