ok so i have a cascade 400 submerged filter, it has a carbon and a sponge filter, but i was thinking... cant bacteria grow on the sponge that can make a biological filter?
or what? only answer if u know for sure!

reendragon wrote:


Sure they can and they will. Anywhere you have an accumulation of waste will have bacteria.

Its actually really important that they do, why its important cleaning them to keep them wet and not use chlorinated water, and why you should never replace all of them at once--to keep the huge colonies of bacteria that grow on pads etc. from dying.

Of course there will be too on tank surfaces and substrate, but the filter is is pretty much the main place where your bacteria will flourish as long as the tank is properly cycled and maintained.

just to add to johnnys post. the carbon will also act as a biological surface, so removing it you also remove part of your bio. carbon should be replaced regular or any thing it absorbs will leach back into the tank.

how am i supposed to wash the sponge filter without killing the bacteria?

just rince in a bucket with some old tankwater.
That will clean any dirt that may clog the spongue, but will leave most bacteria in there.
I only clean my spongues when my flowrate is getting lower.

ohh thanks, but how do YOU take water out of the tank in a water change?

With a piece of tube or a gravel cleaner. You start a syphon. You should be doing weekly water changes of 25-50%

I use a large diameter hose and syphon the water out of the door

x2, i only attach a soda bottle with the bottom cut off to the hose.
I insert the bottle into the water , and let gravity do it's job.

That makes an excellent and cheap gravel vacuuming system.
I can reach the bottom of the tank with the cut off bottle and all debris and dirt will swirl out of the gravel and leave the tank.