move fish to new tank or wait.

Darius Powell

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Nov 6, 2019
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We bought 5 Zebra Danios from a pet store afther they tested our water and gave the all clear. My partner was advised to put the fish in after just a day. She waited 2 days...

We now know this was bad advice as we've sadly lost 2 of the danios. Each died with 4 days of each other.

Knowing something was wrong we've now learnt the tank should've been cycled for a few weeks befor adding fish.

We decided to get a new tank, as the other one was too small (more bad advice) and have started the cycling process adding some food to start bacteria growth and adding filter boost (daily in double dose).

We are 1 week in. Meanwhile I've been doing 30% - 50% changes on the smaller tank, cleaning as I go.

However the levels for the small tank still seem high and I'm concerned it is a bad filter. Below is a current comparison of the tanks. My question is should we wait longer for the cycling or move the fish now? The remaining fish aren't showing signs of breathing problems at present.

Tank big 80l (1 week no fish, added food to help cycle and adding double dose of filter boost daily)
Nitrite 0
Ammonia 0.25
Nitrate 5
Ph. 7.8

Small tank 26l (3 weeks with fish)
Nitrite 1.0 - 2
Ammonia 0.25
Nitrate 5-10
Ph 7.8

Any advice would be appreciated.



Feb 16, 2008
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Do a large (85-90%) water change in the bigger tank. Then move the old filter as well as the fish into the big tank. Run the 2 filters together until everything is stable. The benefits to this are
  1. You don't lost the bacteria that has already built up in the smaller tank
  2. There is more water to dilute the bad stuff.
Continue testing daily and changing water as neccessary. Feed sparingly (twice a week is enough) until the cycle is established. Adding live plants, especially fast growing ones, will help as they use ammonia to grow without producing nitrite or nitrate.

Another benefit to this is once the cycle is complete you can return the small filter to its original tank and add suitable fish (say a betta) immediately as it will already be cycled :)


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