Brackish Water Aquariums
Neither Freshwater nor Saltwater but Water in Between
A brackish aquarium has the easy maintenance of a freshwater tank but allows the aquarist to raise many unusual fish that are native to more salty water.
In nature, brackish water is found where freshwater rivers meet the sea. As you go further away from the sea, the salinity level reduces so there are certain degrees of brackish water along with species that can survive in it.
Salinity Level of Brackish Water
True brackish water is a mixture of three parts salt water to one part freshwater, or 12 grams of aquarium marine salt mixture to one quart of fresh water. Saltwater marine tanks usually contain 4.7 ounces of marine salt per US gallon. A medium brackish tank will have about 2 ounces of marine salt per US gallon whereas a light brackish tank will have approximately 1 ounce of marine salt per US gallon.
The salinity level of a brackish tank should have a Specific Gravity (SG) of no more than 1.021. Full fledged saltwater tanks have a higher SG ranging from 1.021 to 1.026. In a brackish tank the water should be changed about every two weeks. It is important to add salt at these times in order to bring up the levels to where you want them. A hydrometer to measure salinity levels is essential.
Fish Species for Brackish Tanks
In a light brackish water tank (SG of 1.002 to 1.005) you can keep:
- kribensis, glassfish
- live-bearers such as swordtails, platies and mollies (which can be conditioned to live in strong salt water)
- African cichlids because it seems to keep the diseases down and stimulate both growth and breeding
In a medium brackish water tank (SG of 1.006 up to full strength seawater at SG 1.021), you can raise:
- scats
- monos
- archerfish
- Colombian shark catfish
- violet gobies
- sunfish
- flags.
The great Rift Lakes, millions of years ago, were actually inland seas with a high salt content. Over the years this content has lowered to close to actual fresh water. Some fresh water fish actually go to brackish water to spawn, like the fresh water sting-ray.
Plants and Substrate in Brackish Water
Most plants do poorly in brackish water. You could try Java moss or Java fern or water sprite to see if they work. Mangrove roots grow well in brackish water but they are hard to find in stores and are costly. Otherwise, decorate your tank with rocks, driftwood or plastic plants. Brackish biotopes tend to be sandy or muddy so it’s best to use fine gravel or swimming pool filter sand at the bottom of the tank.
Equipment for Brackish Aquariums
- tank that is large enough to accommodate the fish you want. (Some of the above-mentioned fish need large aquariums because they become quite big when they mature)
- filter, preferably not under gravel
- heater, submersibles are the best
- lighting you would use for freshwater tanks
- protein skimmer is optional
- hydrometer that has a lower scale. (Some of them are designed for marine tanks which are based on a higher reading of specific gravity).
Like any new venture in the aquarium hobby, you need to research it carefully. Base your fish selection on adult size, temperament, compatibility and the ideal salinity level.
