Brackish water fish are fish that live in water that is a mix between freshwater and saltwater. In the wild, this is usually the area where the sea meets freshwater rivers and lakes. Keeping brackish water fish in aquariums means you need to add two tbsp of marine salt to the tank for every 10 gallons. That’s the easy explanation. When buying fish keep this information about brackish water fish in mind:
Pet store mistakes with brackish water fish: The problem is that when you go to a pet store, very few sell brackish water fish. Those that do, sell brackish water fish in freshwater tanks. While some brackish water fish can tolerate freshwater conditions, they are healthiest in brackish water. Pet stores sell these fish in freshwater to get you buy them more often. They don’t want you to feel that the fish are too difficult to care for. The sad fact is that most pet stores don’t even know they are selling brackish water fish.
Types of brackish water fish that pet stores sell: There are the fish that are generally found in brackish water tanks in the pet store. Employees should explain this to you when you decide to choose one of these fish. If you see any of these fish in a freshwater tank, do not buy them. If brave, point out to the manager that the pet store is killing their fish.
Monos: These fish have diamond-shaped bodies and can grow up to 10 inches. They are omnivores and can be aggressive.
Scats: These adorable fish are round with spots. They can get up to 12 inches. They are omnivores, but need greens to survive. They will eat up the algae in your tank. Pet stores will tell you that they are aggressive, but don’t listen. Scats are very fun to observe and will watch you as much as you watch them.
Knightfish: These guys will eat smaller fish. You really wouldn’t need more than one in your aquarium.
Mudskipper: These unique creatures need both brackish water and dry land. While they are neat, they are harder to take care for than most aquarium pets.
Brackish water fish sold in freshwater: Here is where the trouble lies. Pet stores commonly sell all of the fish listed here in freshwater. Often, the store doesn’t even know what they are doing wrong. If you purchase any of these fish, acclimate them slowly from freshwater to brackish water.
Puffer fish: Everyone loves these fish, and you probably notice they die quickly. Look in Wal-mart or pet stores and you’ll see most of their puffer fish dead. More on the Green Spotted Puffer fish below.
Columbian shark(Catfish shark): These guys can get up to two feet long, but that’s only when kept healthy in brackish water. It is rare to see them sold in brackish water.
Silver Dollars: When healthy, these guys can grow up to 10 inch round discs. They are omnivores, and will eat all the plant life in your tank. They are always sold in freshwater, but prefer brackish water.
Archerfish: Archerfish are amazing. They need low water, and love to shoot bullets of water out of their mouth to catch flies you put inside the tank for them. The reason they are sold in freshwater is because they are born in freshwater, and then move to brackish water when they are older. Few pet stores will tell the new owner about this, because they don’t know themselves. Archerfish need to be acclimated from freshwater to brackish water as they grow older.
Dragon Gobies(Dragonfish, violet goby): Seeing these amazing fish in freshwater can really depress you. Especially when they are skinny and very unhealthy. Sadly, these eel-like fish are often sold in freshwater. They will not survive, at all. If you see these sweethearts in freshwater, complain to the owner or pet store, please.
Bumblebee Gobies: People love these yellow and black spotted fish, and pet stores know it. They sell them in fresh water so you will buy them. Problem is, that most species of bumblebee goby need brackish water, and some need to be acclimated to salt water.
Two more are the Glassfish and the Needlenose Gar.
Brackish water fish that can tolerate freshwater: These fish are always sold in freshwater, and are very common fish. You will recognize the names, and it would not be surprising if you have many in your home aquarium already. These fish can survive perfectly fine in fresh water, but giving them slight to full brackish water will keep them even healthier. There’s a reason so many of these fish die quickly when you bring them home. All of them make excellent, and easy, tank mates for a brackish water aquarium.
Mollies: Yeah, you have some don’t you? Or you did and they went belly up in a few days. A little marine salt goes a long way.
Guppies: Guppies can survive everything. They are mentioned here because they are brackish water fish, but will do just fine in freshwater. Just watch out for all the babies they like to pop out.
Silver Dollars: These guys were mentioned above, but are added here because they, too, can tolerate freshwater. Really, though, they grow fast and are healthy buggers in brackish water.
Brackish water fish that start out as freshwater fish: Some fish, like the Archer fish, are born in fresh water but move to brackish water. Any fish like this, and brackish water fish sold in freshwater, must be slowly acclimated to brackish water.
Brackish water fish that become saltwater fish: The saddest example of wrong care for fish is the Green-Spotted Puffer. These guys are typically sold in freshwater. They will get ill quickly and die. They need brackish water, but after they become adults, they will need salt water. If you buy these guys you must acclimate them from freshwater to brackish water, and then eventually to saltwater. Good luck. The Bumblebee Goby is another example of this type of fish.
Owner of brackish water aquariums
Starting a Brackish Aquarium, badmanstropicalfish.com
Index of Brackish Water Fish, aquariumfish.net