Brackish Tanks: A Guide To

In this thread I will try to cover and explain everything anyone will need to know on how to set-up, stock, and maintain a successful brackish water tank.
For me, brackish was a break away from the norm of fresh water tropical fish keeping, I had been interested in saltwater for a while. But ever noticed how much it costs to start a marine tank? Well, brackish tanks dont require the considerable cost, the complexity of special equipment, and time devotion that marine tanks do to be successful, but they still offer something considerably different from the average freshwater tank.
Brackish water aquariums allow you to keep many beautiful, interesting but not always commonly seen species. A brackish aquarium can be a mixed community tank, a specialized species only tank or a specific habitat.

Brackish waters occur where rivers and streams meet the oceans of the world. The salinity,measured as Specific Gravity(SG), of brackish water varies depending on the tidal cycle, amount of freshwater from rain or rivers, evaporation, and temperature. The typical specific gravity (SG) of brackish water can vary between 1.005-1.021(these number vary depending on what source you use) where the SG of the ocean varies between 1.022-1.025. There are three types of brackish biotopes (habitats), they are 1) the estuary, 2) the brackish river, 3) the mangrove/swamp. I will discuss these areas in more detail further along, for each one has its own specific characteristics and inhabitants that should be considered when setting up your own tank.

The Estuary Set-Up
Estuaries are formed at the mouths of large rivers that generally have some year round water flow that produces permanent brackish conditions. The estuary biotope maintains a higher, but more constant, salinity(SG) due to its relativity to the ocean, being closest to the ocean than say the mangrove or river biotope. The only times that the SG in estuaries will vary greatly is during heavy flooding or extreme drought.
The estuary set-up is probably the most commonly used set-up for brackish water aquariums. These tanks are easier to maintain, and all that you need to do is have a slow-to moderate water flow, good aeration, and maintain higher SG levels and pH levels. Estuary set-ups are best done with larger tanks (55gal + to start and expect to need a larger one in a few years, depending on how many fish you stock it with) as its normal inhabitants can grow to larger proportions.
The most commonly found inhabitants are Monos, Scats, Columbian Shark Catfish,Puffers and other larger types of brackish fish. Most all brackish fish will venture in and out of the different biotopes, but some fish will be more common in one area than in another.

Specifics for this set-up:
Temperature:78-84 F (I keep my tank at 80-82)
pH level: 7.6- 8.5
SG:as juvieniles 1.010-1.015*(See note below) with a gradual increase to 1.20-1.025 as adults
Decoration: Rocks and branchy driftwood (be sure to clean driftwood)
*NOTE-This SG for juvieniles depends greatly on whether or not your local fish store sells Brackish Fish in FW or BW, please check with your LFS to see what their SG is in the tank with their BW fish, and match your tanks SG to that of your LFS.

The Brackish River
Brackish rivers are at the end of the cycle, or rather the last place that the saltwater flows to. Because of this, the SG is not generally as high or as stable as the estuary. Backish rivers tend to be fast flowing, and because of this are highly oxygenated, and are usually heavily planted along the sides with open swimming areas in the middle.
With the river set-up you will need a higher flow rate of water, this can be achieved by using a powerhead to help create the higher currents, an air stone and air pump to help with aeration, and maintain lower SG levels,and maitain a high pH level. Because some of the inhabitants of the BW river biotope are smaller a tank as small as 10gals can be used for SOME species, but 29-75gal tanks are best suited for this set up, but of course you can set-up whatever size tank you want.
The most commonly found inhabitants of the BW River are: Bumblebee Gobies, Fan Dancer or Knight Gobies, Glassfish (just a reminder, Only Buy UN-PAINTED Glassfish), Celebes Rainbow Fish, Puffers, Orange and Green Chromide Cichlids, Silversides, and many other types of fish.
NOTE: This system usually has a higher concentration of fish due to plant cover and increasd oxygen levels.

Specifics for This Set-Up:
Temperature: 78-84 F
pH Level: 7.6-8.5
Salinity(SG): 1.005*-1.010
Decorations: Heavily planted, covering the sides and top of the water, with swimming area in middle and driftwood and rocks covering the bottom.

*NOTE-This SG depends greatly on whether or not your local fish store sells Brackish Fish in FW or BW, please check with your LFS to see what their SG is in the tank with their BW fish, and match your tanks SG to that of your LFS.

The Mangrove Swamp
Mangrove swamps are found along the sides of estuaries and rivers. Mangrove swamps have low water flow due to fact that they only recieve the excess flow from rivers and estuaries. They usually have a low water level, but do flood during periods of heavy rain, and high tides can also effect the water level of the mangrove swamp. The swamps usually have a mid-high range brackish SG, and is somewhat constant, except for during times of heavy rains or high tides.

The Mangrove Tree is the dominant and most important aspect of the mangrove swamp.
About Mangrove Trees:
The three most common types of mangrove are red, white and black. They are typically slow growing, and some seeds may take up to 5 years before they start to grow. The trees rely on insects to pollinate them, after which they produce their seeds. the seeds actually start to grow leaves and roots before dropping from the tree, which helps to insure their survival.

Mangrove roots are divided into 3 parts:
1)Radiating Cables; The roots that are most recognizable, are the larger roots that suppoprt the tree, provide shelter for fish and other animalsand collect some nutrients.
2)Nutritive Roots; These are small roots that branch off of the main branch of the tree or radiating cables and collect nutrients from the water and mud.
3)the last type is a simple type of root that collects oxygen for the tree.

Mangroves are an excellent exporter of nutrients and is natures own living filter. It is for this reason that many saltwater and brackish water aquarium hobbyist are starting to use them for the main filter on their tanks.

I'm going to mix things up just a little and list some of the inhabitants of the mangroves before going into the set-ups, because I feel this might make things a little easier to understand.The most commonly found are: Fiddler crabs, mudskippers, archerfish, anableps, gobies,some types of killie fish and other oddball fish as well.

The mangrove set-up can be accomplished in a couple of different ways. Most mangrove tanks have both a land area and a swimming area with mangrove trees growing along the edge of the water. Depending on if you are doing a species only tank, or a community tank will have a great effect on what size tank is required. My opinion on this set-up would be that if you are doing a spieces tank, a 20 gal tank or larger should be used. This of course depends on whether or not you are doing a fish only spieces tank or a crab or mud skipper tank. A 30 gal or larger tank should be used for a community tank, whether its a fish only tank or a tank with fish and crabs/ mudskippers. Long tanks would be a better choice for these set-ups than tall tanks would, especially in the smaller tank, to allow more swimming room for your fish.
Canister filters or internal filters work best on this set-up with air stones for extra aeration. The salinity(SG) should be maintained between 1.010-1.015 with a high pH level.

Specifics for This Set-Up:
Temperature: 78-84 F
pH Level: 7.8-8.5
Salinity(SG): 1.010*-1.015
Decorations: Mangrove Trees, floating plants, driftwood/ bogwood and rocks along bottom

*NOTE-This SG depends greatly on whether or not your local fish store sells Brackish Fish in FW or BW, please check with your LFS to see what their SG is in the tank with their BW fish, and match your tanks SG to that of your LFS.

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Continuation of A Guide To


Tank: Most people say nothing less than 30 gals, I disagree with this, there are some brackish water species that will do fine in a 10 gal tank as long as you dont over stock it. But remember, the bigger the tank the more stable it will be.

FILTER: I have found that the best filters are either the hang on the back mechanical with bio-wheel fliters and canister filters for brackish tanks. I personally use Rena XP-3 canister filters on my large tanks with Marineland or Peguin filters as back-ups. You want your water turned around 10 times per hour at least (on a 30 gal tank that would be a single 300 gph filter or 2 150 ghp filters), but I' a big fan of over filtering especially since many of the brackish species are messy eaters.

HEATER: Dont go cheap! Get a good submersible heater, preferably two, one for back-up. Make sure its for fresh and salt ater use. (5 watts of heat per gallon)

GLASS CANOPY/ LIGHTS: It does not have to be a glass canopy but in my experience the glass helps to cut back on evaporation. Since there will be salt in your waterr there are very few plants that will grow in the tank, however there are some and I will touch on them at a later time, but for tghe time being standard lighting should be fine.

THERMOMETER/HYDROMETER: You will need a thermometer, and a hydrometer to measure the salinity of your water. Make sure when buying your hydrometer that it reads as low as 1.001 and reads in .001 increments, if your local fish store doesnt have one that reads that low, check with stores that sell brewing supplies and get one there. Another way of checkig salinity is with a refractometer, they are more expensive that hydrometers, but are more precise and most all of them automatically compesate for water temp.

SUBSTRATE: This is mostly up to you, however brackish biotopes are usually sandy, silty or muddy. A lot of the people I know with brackish tanks use play sand from the local hardware store, I personally use aragonite sand mixed with onyx sand in order to maintain a higher pH level. Avoid thick layers of substrate, as they can build up anerobic gases which can be harmful to your fish.

MARINE SALT: I use Instant Ocean but most any brand of synthetic or natural sea salt should be fine. UNDER NO CIRCUMSTANCES SHOULD YOU EVER USE API AQUARIUM SALT. This is not the right kind of salt for brackish water,I dont care what your LFG said, it does not contain the proper trace minerals and nutients that brackish fish need to lead a healthy life.(For more info on different types of "aquarium " salts see 'Confused Over Salt?'below.)

WATER TEST KIT:As with all tanks your water parameters are very important, therfore a good test kit is needed. Since brackish water is part saltwater and part freshwater, a test kit that covers both SW and FW will be needed. I use Tetra's MasterTest Kit, it contains both SW and FW tests in one kit. The only SW tests that will need to be peformed are for pH and KH (carbonate Hardness). Eveything else will fall under the FW category.

WATER CONDITIONER: Just like allways you need to remove chlorine and chloramine from your water before putting it in the tank. I use API Stress Coat, you can use whatever you want just make sure its for fresh and saltwater.

DECORATIONS: This depends mostly on which biotope you choose to imitate, but silk/plastic plants, drift/bog wood (if it is real wood make sure you clean it really good with hot water, boil it if possible before putting it in the tank) and rocks.

Confused Over Salt?:confused:

Aquarium Salt is Sodium Chloride (NaCl). Also known as common salt, table salt or rock salt. This would include Doc Wellfishes Aquarium Salt and Aquarium Pharmacuticals inc.(API) Aquarium Salt. It does not contain the trace minerals that are essential for brackish and marine species.
(Also want to add as a side note: It isn’t advised to use table salt in any aquarium as it can contain anti-caking agents – to prevent clumping – and these are harmful to fish).
You will notice on the container of most brands of AQ salt, it does say “For FW Fish”

Marine Salt is made up of more elements then I want to list here. It also has buffering capacity (Kh or Alkalinity) to help keep your Ph in high end range (8.0 and above) as is necessary when keeping many BW species.
You will notice on the container of most brands of Marine or Sea Salt, it says “For SW Aquariums”

Brackish Water is basically diluted Ocean Water.

If you use 'aquarium salt' you are not duplicating the conditions native to brackish water habitats. Unfortunately many fish stores will tell you differently and say the Aquarium Salt is just fine for making brackish water. As with anything, do you own research and take what they say with a grain of salt (no pun intended)!!


All the basics of setting up a freshwater tank apply in setting up a brackish tank, but this is how I set my tanks up.
1)Out of direct sunlight
2)Level, sturdy stand
3)Place 1 heater at each end of tank
4) Set-up filter( I only use carbon in my filters for about the first 3 months or so after that I only use the filter floss, ceramic rings, and the foam elements
5)Fill the tank up with fresh water to check for leaks and to check filters.
6)Add dechlorinator to tank, add salt to tank (NOTE only add salt directly to tank during the original set-up proccess never add salt directly to tank with fish in it) Turn on filters and heaters, let run for 24-48 hours,check temp and SG.(Salt content = this amount will vary, I suggest starting off with about 1tbs of salt per gal of water and adjust accordingly, but remember, that most lfs sell brackish fish either as fresh water fish or in fresh water for convenience so its best to find out what SG your LFS keeps their Brackish fish in and get your water as close to that as possible.)
7)Once temp and SG is ok (temp between 78-82), drain off about 1/4 water and add substrate and other decor, remember to rinse really well before adding to tank.Top off water. Let tank run for another 48-72 hrs or until it starts to clear.
8)This is the step where you can start the cycling proccess, You can do a fish in or fishless cycle its up to you, I prefer the fish in cycle myself. The use of BIO SPIRA and some small fish to start with is the prefered method of many for fish in cycling, and I will talk more about the types of fish to use later.

Cycling a brackish tank is much the same as cycling a freshwater tank. There are two basic ways of cycling your tank, The Fishless Cycle and The fish in Cycle. I have personally never used the fishless cycling method so below are 2 links fomr MFT's Freshwater Beginner Stickies on fishless cycling for anyone who wants to try it.
Fish in cycling

Converting from Freshwater to Brackish Water
Converting with fish : This is assuming that you bought your fish from your LFS in freshwater. It is very important that you do not increase the salinity of your aquarium water by more than .002ppt (SG) at a time. Too much of a salt increase will badly stress out the fish and may kill your beneficial bacteria. First of all it is best to pre-mix your saltwater the day before doing water changes, and use an air stone or power head to mix/oxygenate the water. Do a 50% water change, add pre-mixed saltwater to tank slowly. Now, some people and articles say to do this weekly until you have reached your desired salinity, I personally suggest only increasing your salinity monthly to give your fish and beneficial bacteria time to adjust to the increasing salt levels. However you should still do weekly water changes, being sure to match your new SG each time. Then the next month, increase your SG .002 again, continue doing this each month until you have reached your desired salinity.
How to Calculate SG:
Example: 10gal Tank
Starting Water SG Level:1.000
Goal SG Level: 1.002
Pre-mix SG Level: 1.004
Multiply goal SG by 2 since you are doing 50% water change and this gives you what your pre-mix SG level should be, in this case it is 1.004.

For those of you who have read this far and are scratching yor heads I'm not finished yet;) ,I will gladly accept constructive critism, comments and questions. Thanks for reading and I hope its a start to helping those who want to know more about Brackish Water Tanks

EDIT: Iwill also add any credits from articles at the end of this because believe me this is not all in my head, I did need some help

Sorry for having to split it up like this but I can only post a thread of 10000 words or less at a time


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New Fish
Jan 5, 2009
I'm raising freshwater shrimp-- My females are about to hatch out-and the babys have to be in 12-15% salinity- I have a 10 gallon tank -I have saltwater mixed to 30ppt-- my hydrometer dosen't go this low could use any help ya can give me--