Tank transfer

[ImBettaThanCool]

I've been running my 20 gal tank for more than a year now, and in that amount of time, a lot of my fish(there used to be 12 originally) have died (sorry, I know that its a lot of deaths, and I tried my best but the majority died from causes that I'm inexperienced with.) Anyway, there are 4 fish remaining, 2 platys and 2 zebra danios. The 20 gal is now much too big for them, so I'm planning on moving them into a 5 gallon tank that I already have set up, but not cycled.

Now for the question: I bought a sponge filter to use for the new 5 gal, and I was wondering if I had to cycle that filter in the new tank, or just run it in the 20 gal for a month, and that would be enough to cycle it. Would that work? Because after all cycling a tank is really just growing bacteria on the filter right? So as long as the filter has bacteria on it, I can just move it into the new tank without any issues. And of course some of the water from the 20 gal is going into the new one to avoid shocking the fish in any way.

 

[SaraB]

The larger the tank the easier it is to keep stable. I'm not sure moving them would be best. Are both your platys males or females (or 1 of each)? Danios may not be the best schoolers but they still like to be in groups of at least 6.
If you 100% think moving them will solve your problems then yes, as long as your filter pad hasn't dried out then you can use it to establish beneficial bacteria in your new tank. Objects will have more bb on them than the tank water will.
If not we (this group) are always here to help keep your 20 gallon tank going and answer any questions or concerns.

 

[Lokilow]

Moving those guys into a 5gal will then be forcing them into a tank thats far to small for them.
However, the answer to your question is- yes you can put a sponge filter in the new tank for a while to cycle it with good bacterial. It also helps to use some of the water from the old tank as well as substrate and plants if you can.

Ive been doing that for ever and my cycles are setup in a week or so like that.

 

[stephpartin]

I've been running my 20 gal tank for more than a year now, and in that amount of time, a lot of my fish(there used to be 12 originally) have died (sorry, I know that its a lot of deaths, and I tried my best but the majority died from causes that I'm inexperienced with.) Anyway, there are 4 fish remaining, 2 platys and 2 zebra danios. The 20 gal is now much too big for them, so I'm planning on moving them into a 5 gallon tank that I already have set up, but not cycled.

Now for the question: I bought a sponge filter to use for the new 5 gal, and I was wondering if I had to cycle that filter in the new tank, or just run it in the 20 gal for a month, and that would be enough to cycle it. Would that work? Because after all cycling a tank is really just growing bacteria on the filter right? So as long as the filter has bacteria on it, I can just move it into the new tank without any issues. And of course some of the water from the 20 gal is going into the new one to avoid shocking the fish in any way.

I'm not sure if taking the beneficial bacteria from your old tank to your new tank is a good idea until you find out what is causing these deaths. A bigger tank is easier to maintain and zebra danios unfortunately need to be in a group of 6 or more to be healthy and happy.

I know it's a pain but you could do a through cleaning of the 20 gallon and house fish in the 5 gallon until you figure out what is wrong with the 20 gallon. It's what you think is best. You know your fish but that is what I would do)