40 Gallon Breeder Reef Sump Plans

This is my DIY Sump. It is installed under my 150 gal reef tank in a cabinet stand.

This design has been in use for over 3 years now, and there isn’t really anything I would change. It is about as simple as it can be.

I recently removed the sump from the system to clean it, and took some photos.

40 breeder reef sump plans baffle sizes


The sump is made from a new 40 breeder aquarium. It is an Aqueon brand that I bought from Petco as part of their “$1 per gallon” sale.


Large Return Section – This is one of the nicest things to have in a sump design. The return pump can be turned off and the return chamber will hold all the water that drains from the overflow box and display. The skimmer will not overflow due to the water level raising past it’s limit. So I never have to worry about turning off the skimmer for any reason during maintenance.

Minimal Baffles – there is only a 2″ wide space in the middle that is lost to having a bubble trap. Many sumps lose much of their available real estate to having too many baffles.


No weir on skimmer section – This means the water won’t be surface skimmed, and might start to accumulate scum. This was fixed with the addition of a pipe at the end of the post.

Turnover Ratings

My Mag 7 return pump pushes around 550 GPH with my 6′ of head height. The sump runs totally silent and has no sound from trickling or splashing. If you have a higher turnover rate, then noise will be heard first around the filter sock area. This is due to the narrow 6″ weir in that area. This design could run up to about 900 GPH without too much noise, just not totally silent.


The baffles are all 1/4” glass taken from an old aquarium I dismantled. The filter sock tray is made from 1/2″ HDPE plastic (more info below).

Building your own version

One thing to note – this is a general guide when it comes to measurements. While the height of each panel can be copied directly, the width may change in your case.  You will have to get your own tank’s exact measurements, and make any adjustments necessary. This is due to the fact that aquariums are made by hand, and every tank may be slightly different.

Check out the Reef Tank Sump DIY Guide for help with construction. It shows how to properly measure and cut panels. It also shows how to set up and then silicone them into place.

Baffle heights 40 gal sump reef tank

Baffle Heights

The 12” baffle (the last one in the series) sets the height of the skimmer chamber’s water level.

The sump holds as much water as possible during normal operation (about 25 gallons), while still allowing for drainage when the return pump is shut off.

If you are trying to design your own sump, and figure out what size and height to make sump baffles, look to the Sump Design page.

baffle construction reef tank sump


The notches cut in the bottom corners of the baffles allow water to pass under, similar to a raised baffle.

These seem to work well for this tank at the size I made them, however if made slightly smaller they would still work fine.

To see how I cut them, go to the Sump Baffles Construction page.

Bubble Trap

This sump has an under-over series of 2 baffles. This is sufficient at getting rid of the small amount of bubbles that the skimmer occasionally produces (such as when it is cleaned – but only for a day or so). While often seen, 3-Baffle bubble traps are unnecessary and just take up a lot of room. Long weirs and slow flow work best.

Filter Sock Tray

There is a filter sock tray that holds 2 X 4″ filter socks (mine are 200 micron mesh type). The tray is made with 1/2″ HDPE plastic (aka Starboard).

The tray was first cut on the table saw to size, then a router was used to create the rabbet notches on each end. You could also just do a few passes with the table saw to remove the material.

I also used my router to remove some material so the water flows down into the socks better without getting hung up on the “lip” of the socks. This isn’t totally necessary, but it does work better to keep it quiet.

sump design filter socks tray In the the original photo it was difficult to see the shape – I have traced over the edges in Photoshop to show the profile.

With this design, the tray needs to fit tightly. It should not allow any water to bypass the socks.

If the socks get too dirty, water will just flow over the wall to the next chamber.

Whenever you are making a piece like this, it is always a good idea to make a test piece first. That way you figure out your dimensions before you cut your “good” material.

filter sock tray design sump This piece of glass siliconed to the tank simply gives the tray a place to rest on. It’s dimensions don’t matter much.

filter sock tray Again, the shape is a little hard to see so I have traced over the image to better show the rabbet on the front edge.

The holes were first cut with a hole saw drill attachment.  I chose the bit that made a hole slightly smaller than what I needed. I then used my handheld router with a straight bit to inch up the size of each hole, a little at a time. I had a sock on hand to test fit as I went along.  This made for a snug fit for the socks so they can’t float up.

Filter socks in sump The notch on the panel shown allows for the chamber to overflow into the skimmer chamber if the socks clog up.

40 breeder sump under display tankThe sump placed back in the cabinet and filled up. Left to right: Skimmer, Skimmate Container, Heater, ATO sensor, Return Pump, and a Powerhead in the right corner.

Modification to First Chamber

One caveat to only having the baffles in an “under-over” setup is having no weir. This means it won’t surface skim from the first chamber where the skimmer sits. This wasn’t a big deal for the most part because I added a power head to that chamber. This helped reduce surface scum.

After I added a Nitrate reactor to the sump, I was getting a bit more slime and bacteria buildup in the first chamber.

I had thought about adding another baffle to act as a weir. This would have worked well, but I would have lost room in that chamber. It is already quite full with the skimmer and reactor in there. Draining the sump for a week didn’t seem that attractive either.

This surface skimming pipe was the solution. It uses a similar concept to an older protein skimmer design with the use of the wedge pipe. This allows you to adjust the amount of water passing through.

It’s a simple design with 3 parts:

  • A piece of flattened PVC to cover the existing opening in the baffle.
  • a piece of 1.5″ PVC pipe cut at an angle. It was sanded enough to fit in the Tee fitting, with enough clearance to turn freely.
  • a Tee fitting. trimmed on the bottom to form a base with the bottom of the plate

The plate covering the opening doesn’t create a perfect seal. A small amount of water passes around the plate. This is the reason it works.

If it was a perfect seal with a single pipe, then it would act as an open drain. This means it would constantly trip into siphon mode, and create noise.