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I have 2 beautiful shark catfish, about 2 inches, in my freshwater set up. After buying them, I found out that they prefer Brackish conditions I will need to re-home them, on the grounds of the size they reach at least, so I was wondering

A -do they HAVE to be in Brackish water? I'm 99% sure of the answer to this question, in which case my next tank will be brackish

B - How soon should I start going about it?

Any help much appreciated. Thanks

If this fish is Hexanematichthys seemani, then migration only needs to be slow, but should eventually end up at close to 100% marine strength for the full grown adult. One course of action would be to begin migration to increasing salinity once the fish is around 4 inches long. Remember that the specific gravity of fresh water is 1.000, and the specific gravity of fully marine water is 1.023, so, if you migrate in stages as follows:

1.000
1.002
1.004
1.006
1.008
...

separate each stage by around 2 to 3 months, ending at around 1.022 (which is around 98% marine strength). So you're looking at something like a 2 year plus migration period - plenty of time to plan ahead. If you're looking for companions, you'll be looking at similarly large fishes, and fishes that are similarly euryhaline - Scats and Monos being two possible choices. Given the adult size of the fish, you're looking at a LARGE aquarium for long term maintenance, and if you house it with, say, two or three Scats, they're going to demand around 150 gallons. I've seen some big Scats not so long ago at Liverpool Museum in their brackish mangrove biotope aquarium - these fishes were the size of dinner plates!




Panda Catfish fan and keeper/breeder since Christmas 2002

Thanks Calilasseia

They are indeed Hexanematichthys seemani. I was aware that they would reach a pretty awesome size, so I'm looking at getting a large set-up. Good to know that I have time to plan, research and save for it. Lesson learnt - always research the fish BEFORE you buy

The list of potential tank mates in profiles is a little confusing, hence my asking 'do they have to have'. The LFS has these fish in a 150 freshwater tank, with other sharks (Bala and Black), also a fire eel in there (which is why we got ours).

If they can go marine, is it maybe worth looking at getting a marine set-up? So many questions These are beautiful fish though and I want to care for them properly.

Best thing to do is set up a brackish aquarium that will become marine in time ... keep it furnished as a brackish aquarium (which means you'll be stuck with rocks as your main furnishing as im not sure that this fish will live in a more usual marine setup involving corals, whether dead or alive) and work from there.

Once the setup becomes more fully marine, it might be worth investigating if you can make it a kelp type setup and keep some kelp fishes with it ... not sure if Scats will eat seaweeds though!

Mind you, when I say 'a kelp setup', I'm not suggesting you go out an get hold of genuine Laminaria Kelp species and relations to provide greenery in the aquarium, because those seaweeds grow to be HUGE ... Macrocystis pyrifera, for example, grows at 30 cm PER DAY until it reaches a height of SIXTY METRES, which makes it a seaweed the size of a large deciduous tree! Indeed, there are inconfirmed reports that some of the Kelps can grow to even larger sizes - I have an old copy of The Children's Encyclopedia that claims Giant Kelp can reach - wait for it - 500 feet in length, making it three times taller than Nelson's Column!

However, if Hexanematichthys seemani is found in Monterey Bay (it's cited as a Pacific species, so it's possible) then it may well be a candidate for a kelp-type aquarium setup once migrated to near-marine water. You will have fun finding companions for it, because most of the kelp fishes I know of are even bigger than the Shark Catfish - Cyclopterus lumpus, for example, is a 56 cm fish when fully grown, and has a basketball-like bulk to its body, making it far too large for anything other than a public aquarium! Likewise, Heterostichus rostratus, the Yellow Clingfish, is a 61 cm fish, and again a candidate for a public aquarium, not least because it's also a predator that can eat fishes up to half its own size!

For more information on kelp forests and a view of an amazing kelp forest aquarium setup, go here. I somehow think you're going to have your work cut out replicating that aquarium though - the tank is 28 feet tall!

Oh, for more information on the fishes of a Californian kelp forest, go here.


Panda Catfish fan and keeper/breeder since Christmas 2002

Thanks for those links. Some very interesting fish on the second one. Food for thought for sure