Upgrading To A Larger Tank?

Jan 7, 2013
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Good morning everyone,

Today I'll be going to the pet store in order to get a new tank for my fish. Until now I have had a relatively small tank, of about 4 gallons (15L), and I am now upgrading it to a larger one, of around 15 gallons (55L). However, I am not entirely sure I am aware of the process required to transfer the fish to a larger tank, so as to maintain all the parameters the same and avoid cycling the new tank.

In my 4 gallons tank, I have:

8 guppies
12 guppy fry (in a small floating tank)
2 swordtail fish
6 neon tetra fish

+ one Cabomba plant, one artificial plant, gravel (not very much though), a filter, a thermometer and a heater.

I have no idea how the process of transfering the fish to a larger tank goes, can you please help me? I do not want to cycle the larger tank, what should I do in order to have the same water parameters, which by the way, are all normal, maybe the nitrates are a bit over 0, but nothing to worry.
I don 't want any of my beloved fish to die.

Do I need to transfer the gravel first, then the plants? Should I squeeze the sponge from the old filter in the new water so as to move the bacteria in the new tank? Do I put fresh water over the old one? Please give me all the details I need to know.

Thank you!


Smart Homes System Specialist
Retired Moderator
Mar 16, 2010
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Bloomin good job you are upgrading, that many fish in a 15l - sheesh. You're still a bit tight in a 55l, tbf.

Right, the "ideal" process is this:-

1) Get a load of buckets, fill them with water from old tank, net the fish and put them in 2/3 of the buckets.
2) Take the filter media from the filter, and put it all in another bucket.
3) Take your cabomba and put it in another bucket.
4) Transfer gravel, artificial decor and heater to new tank.
5) Set up new filter, put all the filter media from old filter into new filter, cutting sponges up if necessary, and top up with new media.
6) Partly fill tank with old water, from the cabomba's bucket, or any spares that you have. Do not use water from the fish or filter buckets.
7) Replant Cabomba
8) Fill the tank with new, dechlorinated water, at roughly the right temperature
9) Switch heater & filter on
10) Net fish and put them in new tank.

There is no point squeezing the sponges into the new tank water, the bacteria will not come off, they cling on to the sponges very tightly. The only way to move the bacteria is to move the media. It is important that you do not ever let the media dry out, as this will kill the bacteria. However, if you keep the media wet, you have a few hours to complete the process.

Obviously, the fish in the buckets are unfiltered, so it's important to get the process done quickly so they don't poison themselves. The problem that you have is that you only have 15l of water to play with, and a LOT of fish, so you may need to fill some of your buckets with fresh dechlorinated water. Split the fish over as many buckets as you can, so that the ammonia concentration is as diluted as possible.


Nov 19, 2012
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I started with a 10 gallon tank and then added another 10 gallon tank when my Platy's gave birth. I now wish I went 20 gallons or more. I'm still a newbie, so can't help you about stocking, but I'd go with a bigger tank. Rather bigger, than too small.


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