Why can't the aquarium used by cichlids be used for goldfish?

Discussion in 'Freshwater Beginners' started by Kelvinwastaken, Jul 10, 2015.

  1. KelvinwastakenNew MemberMember

    I was told that if I want to convert my 40 gallon to a koi/goldfish aquarium that I should clean my cichlids tank (gravel water and filter) I was wound wrong why I can't just replace the fish since the cycling cycle is complete. That and I'm confuse on what I should do with my bacteria on my aqua clear if I do convert te tank
  2. GenaWell Known MemberMember

    IMO, I'd change the substrate for sure. Goldfish are poopy and a fresh start with gravel would be nice.
  3. Dom90Fishlore VIPMember

    Well for one, cichlids prefer a sandy substrate because they like to dig. I have also heard that a bare bottom tank is better for goldfish..
  4. Et tuValued MemberMember

    You didn't ask, but I just gotta say it, Koi are pond fish, a 40 is just not going to cut it. Two fancy's and you are maxed out. Honestly as long as the tank is disease free , the cycled filter should be ok.
  5. hampalongWell Known MemberMember

    You can just replace the fish. :)
  6. DadioWell Known MemberMember

    If the water is good, then there is no issue. As some have stated, the tank is not for koi long term for sure. Koi grow quite fast and require a pond of 1000g upwards so 2 goldies max imo for a 40g.
  7. hampalongWell Known MemberMember

    To clarify, freshwater filter bacteria are freshwater filter bacteria, period. You can remove any freshwater fish, adjust the water if necessary, and add any other freshwater fish. The bacteria carry on getting their trickle of ammonia, and all is good.

    Think of shop tanks. They can hold different fish every week. And to convert from goldfish to tropical you just put a heater in and wait till it's warm enough. To go the other way you just switch the heater off. :)

    But you cannot keep koi in a 40 gallon or even a 400 gallon tank. Adults can grow 3 foot or more and need at least 4ft water depth for proper excercise. Also if you keep young ones indoors they will grow very quickly because of the extra warmth.

    Even standard goldfish grow to a foot, so they will outgrow a 40...
    Last edited by a moderator: Jul 12, 2015

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