What are wet/dry filters?

[William]

What are they?

I hear some talk about them on the site, and see them all the time in the LFS, and was just curious as to what they are, exactly.

Are they better then a HOB? What type of tank should you use it on? ect ect..

 

[loganj]

A wet/dry is a filter, usually located under the main tank, that provides mechanical, chemical, and biological filtration. They will almost always have a much higher media capacity than any of the HOB filters. You can use them on any type tank although they aren't really recommended for reef tanks due to issues with nitrate production. Go here for a pic of one without the media in it.
http://www.captiveraisedcorals.com/SL-10 wet-dry.htm
A Google search on wet/dry would probably turn up lots of info as well.

 

[William]

I figure they can go on any sized tank, but what size does it make sense to have one?

 

[morleyz]

A wet/dry filter is simply that...the water typically comes in over an overflow box in the tank passes through some mechanical filtration and then trickles over some sort of biomedia (like bio-balls, ceramic rings, etc.). This media is not submerged like it is in your typical canister or HOB. The water is then pumped back into the tank. I believe the theory is that you can maximize your bacteria's oxygen access by having less water.

IME, I don't think there's really any size that you would "need" one for, but bio-filter capacity is much higher in a wet-dry, so you can save yourself some space and have a lot more media options on larger tanks. Also, this is just a theory, but I haven't seen a lot of small sized wet-drys, so that might have something to do with it too.

 

[xxmoorishmanxx]

IME smallest tank ive seen a wet/dry on was a 55 with an exception to a small HOB wetbry on a 36.
JC

 

[Allivymar]

I've been under the impression the HOB bio-wheel filters also fit under the wet/dry criteria. Am I correct?

 

[morleyz]

Good point...although most people don't categorize them that way, bio-wheel filters are definitely wet-dry...

 

[Allivymar]

Ok LOL I wasn't sure for a min there since no one mentioned em. Good to know