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          A 75 Gallon DIY Sump

Why do you have another aquarium underneath the big one?  - I've been asked that question more than once while giving a friend a tour of the fish room. There are so many positive roles a sump plays in a successful reef system that it can be difficult to come up with a simple answer to the question. Why do we use sumps?

  • First of all, it means more water - and more water in a reef is always good! The larger the volume of water, the slower things like temperature, pH, alkalinity, salinity, etc. will stray from the optimum. Also, the more water a system holds, the more unwanted nutrients such as nitrates and phosphates can be present before dangerous concentrations are reached.  It follows that we want the largest sump that space and budget will allow.

  • A sump, in conjunction with an overflow and return pump, provides the perfect mechanism for maintaining a constant water level in the display tank.

  • The process of water passing over the overflow's weir, skims the water's surface. This not only removes unsightly scum, but facilitates the removal of much of the dissolved organics, that tend to accumulate at the air/water interface. They flow, with the surface water, to the sump, where they can be removed, from the system, via filtration, skimming, etc.

  • Surface skimming promotes a carbon-dioxide/oxygen gas exchange.

  • Water movement is never bad in a reef tank. A sump means water movement - from the display tank, to the sump, and back again.

  • Finally, what better place could we find to park our equipment like internal skimmers, filters of all kinds, heaters, and the list goes on.

So, sumps are definitely a good thing. Now, you can buy one, but they are expensive - so I decided to build my own. A DIY sump has a very important advantage over a store bought sump - you can design it so that it is exactly the size you want, and has all the features you want.

I built the sump using exactly the same techniques used when building my frag tank and refugium. As a matter of fact, the sump has exactly the same outside dimensions as the refugium, 48" X 24" X 16" (approx. 75 gallons), and was constructed of the same 3/8 cast acrylic sheet. Rather than take up space here with a description of the details of the build, I'll just direct you to the frag/fuge project. Everything, described there about how the tanks were built, pertains to the sump also.

Here is a pic of the finished sump, just after it was placed under the display tank. It sits on a 3/4" sheet of marine plywood which, in turn, sits on PVC levelers. They keep the ply off the floor so that it won't get wet. I placed a piece of 1/2" rubber foot mat under the sump to protect the acrylic:

The sump

On the near end you can see the two filter socks that are used to pre-filter the water flowing into the overflow area.  The sock on the left (in the pic, above) receives water from the display tank, the one on the right from the frag/fuge tanks

The socks I use are 6" in diameter and 16" long. They have a pore size of 25 microns - many hobbyists prefer 100 microns, which has the benefit of lasting longer before a change is necessary, but I like the way the 25s almost polish the water. To me, its worth changing them once a day - that's what we should be doing anyway.

Here's a close up of the filter socks to show a little of the detail on the sock holder:

Filter sock holder

The platform that the socks rest in is removable and has two 5-7/8" holes to hold the socks.

You can see the three baffles, just to the left of the platform. The water entering the sump flows over the first baffle, which is sealed at the floor of the sump. It then flows under the second baffle, and from there over the third. The baffles are there to stop micro-bubbles from entering the return area of the sump, where they would be pumped up to the display tank - which is not good - micro bubbles make water look cloudy.

Below is a clearer view of the baffles. You can get a better idea of their vertical placement:

Filter socks - 2

The other end of the sump holds the two Reeflo Dart Gold return pumps. The left one is the display tank return - the other pumps water back to the frag tank and refugium. The pic, of course, was taken before the plumbing was completed. The bulkheads are 2" Sched. 80 Haywards.

Dart pumps for the sump

A better view of the Darts. I made a little stand out of white 1/4" expanded PVC and black 3/8" acrylic sheet. I used 1/2" rubber matting (the same mat that I used under the sump) for vibration damping. The Darts fittings are 2" in and 1/-1/2" out. The True Union ball valves make maintenance work on the pumps easy.

Dart pumps for the sump - 2



Caleb says...
I am looking to do a filter sock holder like yours and was wondering how you cut the holes to place the filter socks in. By the way great setup.
GlassReef: Hi Caleb, I use a Jasper Circle Jig (model 200):


It's made for use with a hand held router and is great for cutting circles in almost any material that be cut using a carbide bit. I use a 1/4" straight bit for my work.

16th July 2012 3:13pm
Jeremy Martin says...
Glass Reef,

I totally respect your system, but I do have one question about my set up. I am starting a new 120 with a separate sump and fuge/frag tanks. Can I run a portion of one of my drains to the frag/fuge tank, then the overflow of that tank directly to the return section of the sump.

Thanks for your time. Once again your piece of the ocean is what I am striving for on a much smaller scale.

GlassReef: Yes, that would work fine.
20th May 2012 11:28am
Jack says...
Great setup! Very clean. Quick question, please. You write that your filter socks are 25micron. Is that correct? If so, how often do you have to change them? At that small a pore size I would think a couple of times a day.
GlassReef: Yes my filter socks have a 25 micron pore size - I get them from Fish and Other Ichthy Stuff in Oldsmar, Florida. They do clog up a little faster than the normal 100 micron socks, but it's not too bad. Of course the advantage is very clear water. I find that if I ensure they get changed every day, things are fine.
23rd November 2010 5:50pm

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