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Thread: Converting Estuarine Fish to Freshwater

  1. #1

    Converting Estuarine Fish to Freshwater

    Hello to you all from a new member!

    I have been keeping freshwater (tropical) aquariums for a few years now, & have recently started to think about setting up a native aquarium. I was originally going to stock some local black bream (freshwater or only just brackish) but have been reading several posts where people talk about converting saltwater fish to freshwater (bream, flathead, whiting).

    I live right on a creek in the Newcastle area (so no problems getting the fish!) but i was wondering if anyone might be willing to put up some info on the process of converting the fish.

    My main questions would be about tank filtration (what sorts) and conversion times (hours/days/weeks?)

    If anyone could let me know how they have gone about this sort of thing it would be greatly appreciated.


  2. #2

    Re: Converting Estuarine Fish to Freshwater

    hey mate remember to not take undersize fish.
    also u can by bream in pet shops for like 20 bucks, yellowfin.

    i have never done it before but i am also interested, i heard that u set the tank up with salt water from the sea and gradually add fresh water in once every 2 days.- just take a little salt out then add fresh, there are heaps of methods of doing it. im sure u will get more infomation.

    Australian Native Fish Vids
    Specialize in Terapontida's, Perches, Cods, Gobies & Gudgeons

  3. #3

    Question Re: Converting Estuarine Fish to Freshwater

    Thanks for the reply Cam,

    There are a few commercial fish farms in the area that stock bream (and other natives) off and on, but I have never seen them in any of the local fish shops (apart from a few sad looking barra and overpriced eeltailed cats). Apart from having a native tank with a few nice looking fish I'm looking to try this so I can go through the process of catching my own wild fish for my tanks. It would be cool to be able to say I collected my own fish for my displays, and I suppose i might be trying to save a few $$$ in the process too.

    From what ive gathered it can be done by setting up a tank as per a marine setup, and then simply change out the salt water with fresh over a period of time.

    I'm planning to do this with an old 200L tank, put in an undergravel / reverse undergravel filter (with powerheads), sump with trickle filter, basic protein skimmer, standard flouro lighting, heating etc.

    Basically what i'm not sure about is the time period it takes to change the water over, and also will the filtration be able to handle the change? ie will the biological filtration (bacteria) handle the salt to fresh swing, or will my filtration crash?

    If anyone has any ideas about this, or could simply post their experiences it'd be greatly appreciated.


  4. #4

    Re: Converting Estuarine Fish to Freshwater

    I was in Pet City at Mt Gravatt a few years back, and was talking to the fish guy about the Jacks they had for sale (about 15/20 cm versions). He told me they were line caught in an estuary. The method used to "freshen" them was simply to change the water by 50% gradually until it was close enough to being all fresh.
    So basically they emptied half the salt out and then topped up with fresh and then repeated the process and then repeated the process and then repeated the process.....
    The time between water changes was either 1/2 hour or 1/2 day I can't remember for certain, but the least riskiest would have to be 1/2 day of course.

    Hope this might help you.

  5. #5

    Re: Converting Estuarine Fish to Freshwater

    ive done it with a few fish never lost one caught a "LEGAL' bream took hiw home chucked him in the tank with my mangrove jack was a bit sick for a couple of days then he came good ive had him for a couple of years now quite a caractor has grown to neary 30cm. also caught 4 mullet did the same just threw them in all lived fine was hard to find a food for the mullet they ended up eating bloodworms. the jack took quite a liking to them and lost all but one to the red devil the last one i took back to the river. there a lot of jacks in pet stores with massive price tags that came out of the esturies in qld you can tell theve got red fins the spawned ones are a dark brown with mostly lite coloured fins. a friend of mine tried flathead they will change to fresh no worries but wont eat and eventually die. aparently they only eat unless the tide runs wich is hard to reproduce in an aquarium. there are plenty of nice fresh water fish out there to that can be caught in the inpondments


  6. #6

    Re: Converting Estuarine Fish to Freshwater

    i knew friends that threw some of those lttle spotted scats or what ever they were into their outdoor pond with their natives. pretty much all survived until winter. but the longer the process the better i would say, let the fish get used to the changed water. if i were to do it i would change a bucket every 2 days but ive got no experience on the subject

  7. #7

    Re: Converting Estuarine Fish to Freshwater

    Would it be possible to get a flathead used to freshwater, or would that just be to crazy?
    I Fish, I catch, I SNAG

  8. #8

    Re: Converting Estuarine Fish to Freshwater

    I have a good success at converting herring and 1 bream, have lost a few others though. The bherring look really good in the tank even though they are ugly. Use a 20l bucket and change the water 50% each day, Also have an air bubbler in the bucket, this is the way I've found best. I have heard mixed results with flatead, most successfully converted but refused to eat (?need tidal flow)

  9. #9

    Re: Converting Estuarine Fish to Freshwater

    You can bring bream back from around 24 parts per thousand to around 8 parts per thousand in a couple of hours and still get 100% survival.

  10. #10

    Re: Converting Estuarine Fish to Freshwater

    all the fish in queensland that have size limits on them are only sold in shops if they are DPI breed, shops wont take them of everyday people at the end of the day all saltwater fish need atleast brackish water eventually salt its how it occures naturally in the wild, whitting and flathead wont adapt properly and it causes bone problems quickly down the track, bream and jacks are usually fine until they start to reach maturity then salt should be added slowly back to almost sea water

  11. #11

    Re: Converting Estuarine Fish to Freshwater

    i would have to argue with you there just jack. what you have commented there is crap and nothing but false information. all fish that are bred for the aquarium trade are not even bred by the dpi, probably not even one fish hits the market from there, they all go down the drain after 7 days from hatch. whiting survive down to ful fresh at 12 days after hatch and live happily ever after in that condition. mangrove jack story, well just look at awoonga, this story will make you look like a fool for your statement.

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