40 Long Freshwater Sump Design Help

  • #1
So I'm looking to build a sump for a freshwater 120xH (60" x 18" x 25") using a 40 Long (48" x 13" x 17") or even a 55 as they have the same footprint and should fit comfortably beneath a 60" tank. The only reason I'm leaning towards a 40 is it should be easier to work in as its considerably shorter.

The tank will eventually be home to a harem of Green Terrors, ideally 3-4 females and a male. In my experience so far they can be extremely messy eaters, pumping at least half of the food through their gill plates...Though feeding a little less and switching to Repashy food has helped. So far I have 3 young adults in a 45 gal bowfront.

I'm also hoping to keep the tank at least partially planted, so far they haven't tried to uproot anything, but they have partially buried a few plants.

I also want to move a red cherry shrimp colony from a 10 gal into a compartment in the sump, a grow your own treats type thing, or use it to rear a handful of fry, or an isolation tank or...trust me I can find something to do with it. I figure this section should be approx 20" long.

The pump I plan to use has a footprint of 7" x 4" so I figure 8" for the return section. That should give me enough volume to only top it off once a week or so (I'm planning on covering the sump as well as the display tank).

That leaves 20" for filtration. Currently in my 45 I'm running twin C4 HOB's with Purigen and large prefilter sponges and its working wonderfully, fantastic clarity, zero ammonia/nitrites, and enough plants to stretch water changes into the 2+ week mark without having the nitrates go over 20 ppm. That said I'm going to need pretty heavy mechanical/bio filtration.

As far as mechanical filtration goes I'd like to use something easily cleanable, typically I just rinse my sponges in the water I'm removing for a water change and throw them back in. If they are really plugged I may replace one at a time. Having not used filter socks do these work better? Are they easily cleanable? What would you guys recommend?

For biological filtration the C4 filters have a drip tray with ceramic media, this seems to work well for me but I can see in the future I'm going to have to slowly replace it as it gets filled with gunk. Using a wet/dry also limits the water level in the sump severely.

I don't like the idea of an air pump. Can you use fluidized media such as K2 without air stones, maybe just a re-circulation circuit off the pump? I've never used the stuff, but it seems like it is amazing both in terms of efficiency and low maintenance requirements.

The last option is submerged media, something I haven't really used either. This sounds like the simplest option to set up, but I'm concerned about the efficiency and maintenance.

For chemical filtration I think I could just sandwich a media bag or two in between a baffle, it doesn't seem to take much Purigen to fix up the clarity. I also have the option to run a HOB if necessary.

So then what order do you run the system in? Can you put the refugium first, or should it be behind the mechanical filtration? I suspect the bio and chemical doesn't matter so long as its behind the mechanical?'

Is there anything I missed? Things I should just get rid of? Any suggestions or pictures of working freshwater sumps would be greatly appreciated.
  • #2
giving this a bump up for you, hope you get some responses today
  • Thread Starter
  • #3
I'm actually really liking this guys setup.

I'm just not sure about the sand filter at the beginning, how would you clean something like that? Possibly come up with something involving sponges/filter floss in its place to mechanically filter. Apparently his tank has been running for years without issue though.

The tumbling bioballs look like a fantastic idea.


Actually I see in a later video in his series he uses K1, but it eventually all gets stuck to his outflow on the bottom corner. Does it not stay somewhat buoyant once loaded with bacteria? Could you find a way to use fluidized media with only the gravity flow, without an airstone/powerhead?
  • Thread Starter
  • #4
Alright, did some more research and work and come up with a simplified design.

My goal was to come up with something easily serviceable, simple to build, and contain a large refugium.
Sump V1.png

It has a 24" x 12" x 10" refugium section (12.5 gal), I think I'll try to disperse the inlet flow as much as possible over the area. I'll have to play with it. Maybe just as simple as running the drain pipes into some rock work. I like that its completely on one side of the tank, I'll be able to fit a 16" light to hang over it as well as glass covers to keep splash/evaporation down since the tank has a center brace.

The water flows over a baffle into a 3.32 gal mechanical/biological foam section, under a baffle and into a second 3.32 gal Matrix section before flowing through a bubble trap and into a 4.16 gal pump section. I think the large surface areas of the filtration sections (96 sq. in.) should resist clogging decently well. I might have to deal with some grazing shrimp when I change the filter floss, but that's not a big deal. I might alsohave to put some light diffuser to hold the filter floss in place.

Any additional chemical media like Purigen or carbon would simply be placed ontop of the Matrix.

As far as flood proofing goes, the sump has extra capacity of about 12 gallons which is over 2" of water in the main tank. The 4.16 gal pump section is less than 1" in the main tank, so It should be impossible to flood via clogged drains or power outage, while allowing a lot of options for pumps, though I'm leaning towards a Current USA eFlux DC Flow Pump 1900 or 3170.

I've never done a sump before, is this enough filtration? I think it looks simple to build with glass and light diffuser which should save me some money.
  • #5
Looks good, a few things first if the water drains directly into the refugium all the that comes down the pipes is going to accumulate there, which may be a problem. Second that filter floss area is probably to big. I would reduce it to about 2 inches which should be plenty. You could increase the size of the bio media section but its probably well big enough. I'm planning on a 40 gallon sump but I'm using 2 20 gallon tall with a coupler because I can't get a 40 into the stand. Maybe put 3 inch section for the water to come overflow to the mechanical flow under to the biomedia over to the refugium flow over through another floss section to te pump area. You should darken out the baffles on either side of the refugium to stop algae in the other section.
  • Thread Starter
  • #6
Any reason to reduce the filter floss area in particular?

I've seen most sumps with 2" sections as you say, is this just convention to save space or does it need to be small for a reason? I was planning on stacking 8"x 12" x 1"sheets of foam in increasing PPI. I figure that if I cut and unrolled my cylindrical prefilters on the current tank they would be about 4" x 12" total surface area combined. I just took this and doubled it since I was going from ~400-500 GPH to something around 800-1000 GPH.

I'm not too worried about things coming down into the refugium through the drain as it will be housing scavengers and dense plant growth. My shrimp love to pick over uneaten fish food.

I totally agree on using dark baffles, I'll get as dark of smoked glass as possible. This was actually one of the reasons I wanted to keep the refugium off to one side rather than in the middle.
  • #7
If you using the poret foam they say you need to give 3 inches between sheet of different size because putting one on top of each other increases the resistance to flow. You really don't need that much mechanical filtration if you get some blue and white filter media fold it over should be more then efficient, but you should have some before the return pump. The biomedia can create gunk which you don't want getting back into tank. Also on freshwater tanks you don't need bubble traps.

  • Thread Starter
  • #8
Thanks for your input ounderfla69.

I did some more design work and came up with the following design. Its definitely more complex to build, but I think it should be ideal for what I'm after. I really want to focus on the refugium idea.

The tank arrives in 2-3 weeks.

Sump Front.png
Sump Back.png

What I'm really trying to accomplish is something that looks good, is easy to maintain, and removes nitrates from the water. I've seen several examples where a large refugium, particularly one with floating plants, can process nitrates to keep up with a modest fish load.

This plan has ~360 sq in of refugium floor space, significantly more than most setups. I'm hoping to plant it with a low demand rooted plant like Crypts and use a floating plant like Dwarf Water Lettuce. I already have this working in several lightly stocked tanks. The lettuce is amazing for nitrate removal as it is not limited by CO2 in a low tech system.

The design also should be easy to maintain, two 2" Poret foam sheets make up the bulk of the mechanical and bio filtration, but I also have the option to use a ceramic media in the spaces behind it. These can be serviced separately for convenience, very similar to my twin C4 system currently running, but without the need to re-prime the filter. I left the option to have 4" filter socks should I deem it necessary. Likely just the coarser mesh drawstring type. I think the trickiest part of the build will be drilling that many holes into the dispersion panes of glass. For polishing I can stuff some filter floss into the final baffle just before the return pump.

I know the twin 11.5" x 9.5" openings for the foam seem pretty large, but I think it should be OK, hopefully it goes longer before becoming clogged. An as mentioned before, the shrimp love it.

I also think It's going to look amazing having a 4' wall of plants. It will be a bit more expensive to light, but that's OK.

Splitting the system in half also gives me the option to use a divider down the middle if I ever need to separate some fish temporarily.
  • #9
How did it come out? I have gotten a different tank stand and am going with with a 29 gallon doing 2 sections first is a mechanical the second will house heaters, a CO2 reactor and a tetra pond box full of biomedia.
  • Thread Starter
  • #10
Still waiting on the tank. So no construction as of yet. I did do some practice/test cutting of the glass and have updated the design. It got a little more difficult to cut, but easier to assemble. Also should look way cleaner.

A diamond bit holesaw and diamond blade angle grinder blade make the openings possible. Simply drill out the corners then cut a cross with the angle grinder then score and snap the triangles out.

A dremmel with a fine grinding wheel allows you to bevel and fine tune your cuts.

Sump Front V2.png

Sump Back V2.png
  • #11
Wow your able to cut holes in glass like that without cracking it, I'm impressed! I would do it with acrylic but not with glass.
  • Thread Starter
  • #12
Yeah, I was amazed too! I mean I've done similar cuts with tile, so why not glass? Really so long as the tool takes very tiny bites and you lubricate it with water it seems to work well.
  • #13
Looks like an interesting design.
  • #14
Any update??
  • Thread Starter
  • #15
No, unfortunately I'm still waiting for the tanks to arrive. Apparently they were shipped to the wrong warehouse by the distributor.

On the plus side they are in the back of my Father's SUV, should arrive tomorrow night.
  • #16
Well keep us updated
  • Thread Starter
  • #17
They're here! After so much delay they're here, and in one piece!

Going to start on the stand first, sump to follow.


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  • #18
I use Seachem pond matrix in my sumps. It's cheaper than the regular Matrix and works great.
  • #19
Any update?

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