# Double Filtration?



## Rick_Lindsey (Aug 26, 2002)

This is more of a "filter theory" question than DIY, but since the application is almost certainly going to be DIY I thought I'd ask it here.

Suppose I've got a sump with a wet/dry filter, and a return pump that sends half of the water back to the tank, and half of the water back into the wet/dry filter for a second pass.

Does that second pass through the filter actually accomplish anything? Is it equivalent in filtration power to sending all the water back to the tank? Is it equivalent to a regular system with half the flow rate?

I suspect the answer lies somewhere in the middle, but I don't know enough about how quickly the bio filter does it magick to be able to tell how effective (or ineffective) such a setup might be.

-Rick (the armchair aquarist)


----------



## remarkosmoc (Oct 19, 2005)

interesting. I have no idea biologically but I think you are correct when you say the answer is somewhere in the middle.

You would be moving the water around more and thus get better oxygenation i would think.

opcorn:


----------



## Mcdaphnia (Dec 16, 2003)

Some would imply that a bypass is a bad thing.

http://www.magnavore.com/closerlook/wdcl.html

But I'm not sure they actually say it, just let you assume it is, advertising psychology.

Certainly there is a flow rate needed in the wet/dry media for ideal dispersal and oxygenation that could be different from the flow rate you want inside your aquarium. Splitting the flow makes perfect sense in that case.


----------



## Rick_Lindsey (Aug 26, 2002)

Mcdaphnia said:


> Some would imply that a bypass is a bad thing.
> 
> http://www.magnavore.com/closerlook/wdcl.html
> 
> ...


Hehe, in my case I'm considering using a SCWD to get a "surf zone" effect but don't think I have enough room to set up multiple spraybars since I really only want the agitation on one end of the tank. Routing the other output of the SCWD back to the wet/dry seemed like reasonable compromise and less wastefull than just leaving it open to stir up the sump .

-Rick (the armchair aquarist)


----------



## Rick_Lindsey (Aug 26, 2002)

double post. oops.


----------

