Changing Gravel

[tttnjfttt]

I was under the impression that the bacteria grew on the gravel, not under it

 

[WILDER]

I've always been led to beleive it under the gravel, but not sure.

 

[tttnjfttt]

i've always been told that the bacteria needed somehting to grow on, so its either teh spounge in the external filter or the gravel. I don't know if this helps or not, but i've seen plenty of brown murky junk come off of filters when i shake them out, but i have never had a cycle from it.