Blue Eyes and Bumblebees...a brackish stocking evolution.

Yes, I admit a tiny bit of obsession over my latest botanical-style brackish water aquarium...You know, the one I've been promising to deliver for the better part of the past year...Yeah, that one!

I mean, this thing sat dry for so long that the wood probably cured by mummification! 

I must admit that the "self-inflicted" delays on the launch of this tank have made its ultimate transition from dry diorama to aquatic microcosm among the more satisfying tank adventures I can recall in recent years! Just getting it wet was sort of emotional!

And of course, with the startup of the aquarium came a lot of questions from other hobbyists- the usual litany of stuff like what materials i used, how I filter it, etc...and of course, the most important of all to a fish geek, "What are you gonna put in it?"

And funny, that turns out to be one of the best questions of all. And among the most difficult for me to answer! Oh, I had a vision for a killer brackish tank...I knew some of the fishes that I wanted- Halfbeaks, a few Scats, Archerfish...a lot of "cliche" stuff, but in what I knew would be a very realistic and functional habitat for them...And of course- reality set in when I forced myself to accept the fact that at 40 gallons, the aquarium would place significant limitations on what I could keep there!

Well, there were two fishes on my target list that I knew would fit into just about any size...The "Neon Blue Eye", Pseudomugil cyanodorsalis, and the adorable "Bumblebee Goby", Brachygobius doriae! Right out of the gate, I knew that combining these two faves would not only create a perfect display in this tank- it would immediately and forever disqualify me from entering into one of those biotope aquarium contests, as these fishes are found thousands of miles from each other and would simply never encounter each other in nature.

Too bad, but that's life.

And knowing that I have a cube-shaped 40 gallon tank really cemented home these guys as keepers. They are small, interesting, occupy different water strata, and are both amazing fish to keep in groups. It was one of those "compromises" which really wasn't a compromise! In fact, I think I could hardly have come up with a better combination, given the configuration and limitations of this aquarium.

One of the things a lot of people ask me is, "Are you only keeping those two species in there?" And the answer is...most likely, with the exception of one or two other possible fishes; perhaps another brackish water goby species and maybe, MAYBE the Glassfish, Chanda sp. Part of the decision will be based upon availability of the right specimens, the status of my aquarium at the time- and if I feel that they are going to be "necessary."

You know, the usual stuff.

And it just so happens that these fishes really are working well together in this aquarium!

The Blue Eyes tend to stay in the upper/top part of the water column, with and endless activity level that is completely engaging. And the neat thing is that they will swim at all levels of the tank at any given moment, but they seem to be preferentially a surface dweller. And their subtle, metallic coloration and diminutive size makes them look just fantastic in this sized aquarium.

P. cyanodorsalis is a fascinating fish for a brackish water aquarium, not only because it's a Rainbowfish (which automatically makes it cool), but because it is a "poster child" for the "euryhaline" adaptability. It can live in freshwater, brackish, and full-strength marine habitats/water conditions, and can move between the two quite quickly and dramatically. Many wild populations are subject to rapid tidal influxes and changes, often going from near-pure freshwater to even higher than typical marine (1.025) specific gravities (I recall reading about some specimens being collected from specific gravities as high as 1.030!). That's salty!

Another cool thing about this fish is that it is often found in large aggregations associated with...wait for it...mangroves!

Yup, this little fish is perfect for the habitat which I am trying to replicate, a thicket of mangrove prop roots with lots of small fishes living among them. And since these are small fishes, topping of at around 1.5"/40mm, and live in aggregations, keeping a colony of these guys in a replication of their environment, you'll get to enjoy their interesting habits and reproductive behaviors. And the small size gives your tank a good sense of "scale", IMHO!

To me, there is something extremely interesting about small fishes in a medium to large-sized aquarium, and the other resident in our brackish aquarium, the Bumblebee Goby, is perfect for this type of display!

The 'Bees come from Malaysia and Indonesia, and although long regarded as a "prototype" brackish water fish, are found in all sorts of habitats- including soft, acidic  blackwater niches. Now, in my experience, it's pretty difficult for the typical consumer to know for certain if his/her specimens came from a brackish or soft, acidic environment, so obviously you should ask your supplier. 

Now, in my experience, if you're not sure about the exact water conditions under which your specimens were collected, and your intent is to acclimate them to your brackish water aquarium, you simply need to do it very slowly, over the course of weeks or even months, gradually increasing the specific gravity until you hit your desired target.

It's also long been known that these guys are surprisingly social fishes, excellent for maintenance in small (or medium-sized) groups in aquariums. Males will establish little "territories" and defend them from intruders...It's funny to see a 3/4" long fish chasing away a rival which strays into his self-proclaimed territory. And fear not, little harm ever seems to come from these encounters. 

I was really excited to include a good-sized group (20) of these small gobies in my brackish water display. Again, they are often associated with mangrove roots and the substrates associated with them. The beauty of a rather complex "matrix" of mangrove roots is that they create "territories" for these little guys, which will help diffuse any real "violence" as a result of defensive activities.

And of course, mangrove leaf litter, shells, and open substrate provide these fish with ample areas for foraging, resting, and social interactions. Population density is a big factor in determining the social order of your Bumblebee goby community, and personally, I wouldn't stock an aquarium with anything less than 6-8 specimens (assuming you have the space) to foster these cool social interactions and behaviors.

I've found that not only do these fish tend to stay in the interesting little areas you create in the tank- they will happily-and surprisingly- swim high into the water column to go after food, and simply "explore. Yeah, they're lousy swimmers, but they get the job done! 

So, my rationale of "small and cute" in a decently-sized tank is working out nicely, creating a display that has activity at a variety of levels, with some very interesting social interactions. You'd think that having just one or two species in an aquarium would be less than thrilling- but I think my little exercise is proving my thesis that if you select the RIGHT fishes for the aquarium you've created, it can be engaging and completely engrossing! 

As this aquarium evolves, I have learned to appreciate all of the little details of the environment, and how the resident fishes take advantage of them. It's very interesting and gratifying to design your system not only to replicate a natural environmental niche, but to create an aquascape that is both aesthetic and functional.

And its REALLY gratifying to see the fishes utilizing the aquascape in a natural and relaxed fashion...Something that we've played with in blackwater tanks for a while now, too- and something that is an important consideration when designing and setting up our systems.

So, there is a quick look at the stocking decisions and mindset of this brackish water aquarium. Hope it gives you some ideas!

Stay creative. Stay bold. Stay educated. Stay observant. Stay enthralled...

And Stay Wet.


Scott Fellman

Tannin Aquatics 

Scott Fellman
Scott Fellman


2 Responses

Scott Fellman
Scott Fellman

November 01, 2018

Hi Alex,

The old expression, “If you can’t beat ’em…” LOL

I have not tried Pom Pom crabs in brackish before. There is a “Pom Pom” crab I’ve kept in reef tanks…I can’t recall the scientific name off hand, but would imagine it’s a common name ascribed to 2 totally different species? Do let us know how your tank works out!


alex grinager
alex grinager

October 31, 2018

Interesting to see someone doing just what I am starting up. I have a 29g half filled with rocks and aragonite gravel, awaiting P. cyanodorsalis. Other than some baby black mollies that came from the two female mollies-must have been some fooling around before I bought them-there will shortly be some Bumblbee gobies . I have about a dozen mangroves growing in the tank now. The main reason for setting up this brackish tank was to grow mangroves-I am also a plant freak as well as a fish-freak. Why not combine both passions. Have you tried pom pom crabs-supposedly brackish. Don’t know how they would fare with the gobies.

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