Rainbow Shark Killing Tank Mates? Help

Discussion in 'Freshwater Fish Forums' started by Adam85, May 10, 2019.

  1. Adam85

    Adam85New MemberMember

    I have had a rainbow shark in our tank by himself for a few weeks now. We have tried putting a dalmation molly, a female betta, and 3 glofish with him and all have died. I thought it was the betta so I removed her and then tried just the glofish and shark and now all the glofish are dead. Could he be killing the other fish?
     
  2. nikm128

    nikm128Fishlore VIPMember

    What size tank?
     
  3. Kiks

    KiksWell Known MemberMember

    What size is the tank?

    edit: nikm128 beat me to it.
     
  4. OP
    OP
    Adam85

    Adam85New MemberMember

    20 gal
     
  5. Kiks

    KiksWell Known MemberMember

    The rainbow shark needs a much larger tank.
    Have you tested the water?
     
  6. OP
    OP
    Adam85

    Adam85New MemberMember

  7. nikm128

    nikm128Fishlore VIPMember

    Yes that tank is on the small side for a rainbow. That alone would cause aggression issued
     
  8. Kiks

    KiksWell Known MemberMember

    Online anything from 30 to 55 gallons is advised as the minimum.

    In a cycled tank there should be nitrates. When was this tank set up and when did you add the fish?
     
  9. OP
    OP
    Adam85

    Adam85New MemberMember

    Tank has been running for around a month. The shark was the first one added at about the 4 week mark
     
  10. Kiks

    KiksWell Known MemberMember

    So the tank has been running for around four weeks... so you just added the shark? In your first post you said you've had him for a few weeks, so a little unsure about the timeline here.

    How did you cycle the tank? And have you been testing the water during the cycle to make sure you've had nitrites peak and everything?
     
  11. OP
    OP
    Adam85

    Adam85New MemberMember

    The shark has been doing fine for around a month. Along with the female betta. All my other fish are dying.
     
  12. Kiks

    KiksWell Known MemberMember

    Did you cycle the tank prior to adding the shark?
     
  13. OP
    OP
    Adam85

    Adam85New MemberMember

    Yes. If it wasn’t fully cycled how could those two fish survive?
     
  14. Kiks

    KiksWell Known MemberMember

    Lots of fish can survive less than ideal water parameters. Whether or not a tank is cycled cannot be determined by whether or not the fish are dying. However in your case some of your fish are surviving and some are not and usually when fish die it has to do with water parameters. In this case it could also be because of the shark being more aggressive than usual from being kept in a too small tank. Either way you need to make sure your tank is fully cycled by testing with a liquid test kit and you need to bring the shark back to the LFS or buy a larger tank.
     
  15. nikm128

    nikm128Fishlore VIPMember

    To me, that indicates that your current fish are adjusted to water that is potentially less than ideal. While the new fish can't adjust in time
     
  16. OP
    OP
    Adam85

    Adam85New MemberMember

    I’m testing with the api kit
     
  17. SeanyBaggs123

    SeanyBaggs123Well Known MemberMember

    Does the shark have any where to hide? Can we see your tank?
     
  18. OP
    OP
    Adam85

    Adam85New MemberMember

    Yes he has a set of barrels that he likes.
     
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