Old cycled filter and new filter in new tank

[Linda N]

Hi - I recently set up a new 20 gallon tank and moved all of the residents from a 10 gallon tank into the 20 gallon, along with the filter, wood, ornaments and other décor from the smaller tank. I did not move the gravel as I moved fish from 2 smaller tanks - a 3.5 gallon and 3 gallon - into the 10 gallon. In the new 20 gallon tank I have the filter from the cycled 10 gallon, along with the new filter that came with the 20 gallon tank. They are right next to each other. Can anyone give me an estimate on how long it might take for the new filter to develop a great enough population of bacteria to where I can remove the filter from the 10 gallon? The fish population is exactly the same as it was in the 10 gallon. Since I moved them a few days ago I have tested several times and ammonia and nitrites are still hanging in at zero. I usually change out half the water once a week.

 

[Colin_T]

filter bacteria can double every couple of hours.

take half the filter media from one filter and put it in the other filter. Then wait a few days and you can move one filter out.

if you don't add any of the old media to the new filter, it will take about 4-6 weeks for the new filter to develop the filter bacteria.

 

[Linda N]

Thanks - the two filters are so different in design I don't think I can get the media from the old one into the new one - so I guess I'll wait 6 weeks to remove the old, cycled filter from the other tank. It's been a real learning experience!