Why you like wet-dry?


Guru Class Expert
May 23, 2009
Hi, I'm thinking about filtration types for my next planted tank.

It seems you like wet-dry sumps better than canister filters.
And since plants helps biological waste issues already.
So biological benefit of a wet-dry doesn't seem to be your interest.

So why do you like the wet-dry sump much enough to tolerate the look
of having an overflow box? (Harder-to-clog mechanical filtration?)

You also said about sealing the wet-dry sump to preserve CO2.
But then what is the benefit of having a wet-dry while there is no O2
to contact the water (or is there?). A regular sealed wet-only sump
should be as good?

My main interest in a sump is just to have a place to put an airstone
for nighttime aeration. (Now I'm back to using it again, fishes like it
very much). Putting it in the tank makes ugly stains and interferes with
water flow.


Tom Barr

Staff member
Jan 23, 2005
It can go either way, for larger tanks mostly due to evaporation and equipment out of the aquarium, I prefer wet/drys.
I do not use sumps/sock filters etc but use the wet/dry section to regas the degassed water back into the water.
This saves more CO2 and is about equal to canisters as far as degassing as long as the wet/dry chamber is sealed up good.

Surface extraction is good, keeping shrimp out is tougher.

I think a simple night time powerhead/Hydor wave maker pointed at the surface to cause ripples will help more.

Tom Barr


Lifetime Members
Lifetime Member
Aug 25, 2006

If you're injecting CO2, I agree with you that you may as well ditch the wet/dry section and just sump it (which I like more than a canister for the reasons below). But if you are not injecting CO2, a wet/dry is still advantageous for the gas exchange.

Also, one of the cool things about a sump is that any shrimp that pass through the main tank's prefilter/overflow will just get a chance to grow out in the sump anyway.

Also consider you'll bring in air from the atmosphere from the lower pressure of the drain pipe (even with a Durso design), and so I'm not so sure your airstone is necessary. There's other advantages to using a sump, though I would suggest you take the extra step and make it a fresh water refugium. I hope it's not rude to cross post the below, but it's just a synopsis of what I think about sumps, wet/drys, and fresh water refugiums:

Planted sumps ('fuge moving forward, because it really does help to look at them as SW folks do theirs) are advantageous in more ways than you point out and the obvious (hides gear, more volume=easier dosing/stocking, etc):

1) One can run a reverse photoperiod between the main tank and fuge, keeping dissolved O2, CO2 and pH pretty close to stable.

2) Constant water height in the main tank! This is so huge it needs caps. Super easy water changes by removing the drain pipe leading to the sump, feeding it to some bucket, and then just dumping water into the sump.

3) Fuge is an excellent place for plant, fish, or shrimp growout. Also acclimation.

4) Personally, I think a low tech tank with a wet/dry sump to maintain dissolved CO2 at a level close to atmospheric CO2 may be the NPT of the future.

5) I prefered to dry dose into the sump, which is the prefect dry dosing container, but your drip idea is appealing, too.

Tricky ****:

Using a modified Durso standpipe or other drain can keep noise down while effectively surface skimming the main tank, a big deal for open top folks. I prefer this to your overflow idea because I believe it has less chance for failure (I drilled my main tank myself for this reason), but Durso is also prone to be noisy. You lose more CO2 than you'd think in the baffles of an overflow.

Prefilter on the main tank can be hard. Window screen was the best in my experience.

Leave the return piping so high in the main tank that power outage has minimal return to the tank.

In my time with the above set up, I converted my sump from a sump to a fuge to a planted tank to a paludarium. I think about running a sump again sometimes but if I did it again I'd do it in some super tall tank as a sump and pull it from under the main tank, making it a central point. Like a 24" cube tank would be slick.
If curious, the build journal of the now dead paludarium as a sump design is here: http://www.aquaticplantcentral.com/...ulture/9469-emersed-growth-set-up-advice.html (my old username on APC)

I hope this helps.


Lifetime Charter Member
Lifetime Member
Jan 15, 2009
Surface extraction is a big plus for this. I've had no ends of trouble with thick surface scum due to the foods I use without a LOT of surface agitation. Surface skimming ends that wory with the overflow box. Constant water level means no surface scum line on the glass of the tank as well which is good for viewing. It also means that I won't have that annoying water pouring sound I get with the cannister filters as the water level drops and exposes the spraybar. And there's the usual bits about stuff staying out of the tank and the easy addition of chemicals and such so everything dissolves well before hitting the tank and so on. Drawbacks include the fact that you will use more power than a cannister due to head pressure when running from a sump under the tank back up. You can get around that somewhat depending on where the sump is, but there's probably not much you can do about that.

Just a quick note that you CAN get an overflow box quiet without a durso design which dumps a lot of air into the system causing outgassing. It's a pretty easy design and works very well but you will need TWO outlets from the overflow box in order to do this. If there's interest I can try to upload some photos and an explanation in another thread. Due to the lack of air injection which would cause outgassing, I'm not sure it's as solid a requirement to seal the dry section of the filter but when I move the unit to the larger tank I am likely to do so anyway. Just in case.



Guru Class Expert
May 23, 2009
Thanks for the info everyone. :D

Well, hehe :p , I'm steering toward all canisters.
Because I've just found a slow-flow powerhead
that can be run inline to use at night as additional
aeration which is available around where I live: the Resun King-1A
(still a bit too powerful for the job but better than nothing).

Before, all inline pumps available here were too powerful
and I don't want to put powerhead in my tank.
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