How To Tell If 2Nd Filter Is Cycled.

[Fish are friends]

My 60l community tank has a fluval u2 filter which has been cycled for almost 2 years now. about 2 months ago i set up my Ehiem 2213 external in the tank to start getting it cycled to eventually remove the internal altogether... I want to know, how will i tell if the external is cycled...
I did a water change today and cleaned the internal (which was pretty clean considering i havent touched it in 4 weeks) i squeezed the sponges into the top of the open external and im thinking of just placing them in the filter too so if i ever need mature media i have some!!!
I dont want to turn off the internal yet cause i want to prevent fish loss so whats the best way to tell if i have a cycled filter?

 

[the_lock_man]

My 60l community tank has a fluval u2 filter which has been cycled for almost 2 years now. about 2 months ago i set up my Ehiem 2213 external in the tank to start getting it cycled to eventually remove the internal altogether... I want to know, how will i tell if the external is cycled...
I did a water change today and cleaned the internal (which was pretty clean considering i havent touched it in 4 weeks) i squeezed the sponges into the top of the open external and im thinking of just placing them in the filter too so if i ever need mature media i have some!!!
I dont want to turn off the internal yet cause i want to prevent fish loss so whats the best way to tell if i have a cycled filter?

As far as I can see, the only way to tell if the external is cycled is to run it solo, and monitor NH3 and NO2 levels. But if you put all the media from the internal into the external, then it's job done, cos all the bacteria are moved from one to t'other.

 

[KittyKat]

Without removing it and testing it on a known quantity and concentration of ammonia, you can't. Normally, I assume that running a new and established filter in parallel for 6 weeks is a good minimum for the new one to be considered cycled. Otherwise, the way to "instantly" cycle the new filter is to move all the old media into it.

 

[Fish are friends]

I'll play it safe and take the media out of the internal and place them in the external.. the one good thing is that if the external breaks, i have mature media to place back into the internal.. (2 birds one stone comes to mind lol...)