This article originally appeared in Marine Fish Monthly magazine Volume 11 Number 7, August 1996. Copyright 1996 Publishing Concepts Corp. All rights reserved. Permission to reproduce is granted by the publisher and the author to The Breeder's Registry and is not transferrable.

The sight was almost mesmerizing. I looked downward into a concrete box some 10 feet square. A water flow rate of perhaps 1,500 gallons per minute rushed into the structure and slowly filled it. When it seemed the box would over flow, a hiss of escaping air drowned any background noise and the water movement became violent as the box quickly emptied. Near the bottom, maybe 10 feet below ground level, were pipes that were exposed briefly before being covered by the incoming water. A slurping noise accompanied the spectacle and added a hint of danger. I stepped back, not wishing to fall into the pit.

I am describing a scene from an old wastewater treatment plant on the outskirts of Atlanta.

The plant was demolished years ago but the sight of a device called a "bell and siphon" (or dosing tank) are still vivid. Little did I realize these devices would one day be down-scaled and offer something of interest to the reef aquarium hobbyist.

Today, the bell-and-siphon for the aquarium is known by several names. One of them is the "Carlson surge device", CSD, for short - named after Dr. Bruce Carlson. He installed one of these devices on a display tank in a public aquarium in Hawaii. At least one manufacturer builds relatively small surge makers for home aquaria.

If the hobbyist has a few minutes and a few dollars, he can construct a surge maker. I must warn the hobbyist that this thing is not for every aquarium. They are intrusive in appearance. In fact, they're ugly. And like their industrial cousins, they're noisy. But they can create incredible water movement in the aquarium. I recently built and installed two of these things on my six-foot long reef aquarium. I was so impressed with them, I removed a "dump bucket" that had been in service for over 6 years.

I had attempted to build a surge maker a couple of years ago based on a design shown in a water reclamation reference book commonly known as "The New York Manual". I could not get the device to work and I abandoned the project. I saw a schematic on a very similar device in Delbeek and Sprung's "The Reef Aquarium", but wasn't motivated enough for a second attempt. It wasn't until I saw a surge maker in action at John Lipsey's Shark Bay Aquarium in Atlanta that I was tempted again. John had constructed this deceivingly simple device from just a few parts and installed it on his Acropora tank. When I saw it, I was taken back through the years to the scene at the reclamation plant. I was mesmerized again. I saw in the tank fully expanded Acropora, Stylopora, Porites and other stony corals (see photo). I had to have one (or two). I rushed home and, within minutes, built a prototype. And it did not work. I decided to write this article for two reasons: 1) to assist those interested in good water movement and 2) help those so inclined in avoiding some of the frustration I went through.

Water movement is often mentioned as a critical factor in success with a reef aquarium. Amazingly enough, most hobbyists believe one or two powerheads produces sufficient water movement. In many cases, especially if the aquarium is small and contains only soft corals, this sort of set up is okay. However, for large colonies of SPS (small polyp stony) corals, this simple arrangement will not create sufficient current and may cause the death of the animals. A surge device is a good addition and may well make the difference between success and failure.

I will describe building a 5 gallon surge generating device. Certainly, the size can be scaled according to your aquarium's needs. Just be prepared to experiment. Small things that do not appear significant can profoundly affect performance. Discharge pipe size, height above the aquarium, flow rate into the bucket, along with other parameters, may need to be adjusted. I would strongly advise building a prototype or two when scaling this device to size.

Perhaps the easiest way to deliver water to the bucket is to place a small submersible pump in the aquarium. This way, some of the problems can be avoided. But perhaps the best way is to use a more powerful pump. (I use a MDSC-4 Little Giant pump plumbed into the sump.) This will create a few problems. The scenario is as follows: The pump takes water from the sump and pumps it to the surge bucket. The water level in the sump will fall. When the surge device is full, and discharges, a rush of water enters the aquarium. The aquarium must hold this water as it drains into the sump. If the overflow drain is too small, a real possibility of the aquarium overflowing exists (along with the domino effect, usually in this order - wet carpet, angry wife doctor bill, etc.). The sump must be large enough to hold the influx of water while the pump plays "catchup". The sump must not run dry in order to avoid pump damage. So, the size of the sump is an important consideration and may dictate the size of the surge device.

These are the parts needed:

1 - 5 gallon bucket w/lid
1 - 1 1/2" bulkhead fitting and pipe
2 - 1/2" fittings and pipe
1 - 1/2" 90 degree ell
2 - 1 1/2" 90 degree ells
1 - 1 1/2" 45 fitting

Hardware to hang the bucket from the ceiling (Optional- small surge devices may be placed on the top of the aquarium)

When assembling these parts, be careful to cut the holes far enough from the side of the bucket to allow threading the bulkhead components together. A dab of silicone cement on the bulkhead gaskets will ensure a water-tight seal.

The drawing shows the dimensions of this 5 gallon surge-generating device.

The lid will keep water from splashing out of the bucket and will keep dust and other debris from getting into it. It will also dampen the noise of the siphon breaking.

The overflow is a strongly recommended option. Although these devices seem to be fail-safe, there is little doubt that an overflow could be disastrous. Use a pipe from the bottom of the overflow to the aquarium - but do not submerse the end of the overflow tubing - the object is to allow the bucket to drain. Do not make the overflow work against the head pressure of a submerged tube!

If the device never breaks siphon, then the hobbyist is advised to examine the flow rate into, and out of, the bucket. Water is either being added at too high a rate or the effluent pipe is not carrying water out of the bucket fast enough. A smaller pump may be needed or the flow can be throttled by an inexpensive ball valve. Of course, a second surge bucket can be added to handle the "extra" flow.

The hobbyist should be aware that this type of surge bucket (I can't speak for the commercially available models) will add lots of bubbles to the aquarium. Is this really bad? Air bubbles will lessen the amount of light reaching your corals; the bubbles appear bright because they reflect light. The lighting fixture will become coated with salt spray unless it is raised a few inches higher. of course, this lessens the amount of light actually reaching the aquarium. Also, corals and anemones will ingest the air bubbles but apparently no harm is done. On a more positive note, these bubbles will probably strip the water of waste products, just as a protein skimmer does. Overall, the very positive effects of increased water motion will likely outweigh the drawbacks. Note - a small air relief hole may be drilled in the discharge pipe below the water surface. This allows some air to escape before the rush of water follows. Do not drill the hole so it is above the water surface -it will not work!

The velocity of the water exiting the devices I built is around 4 feet per second. This velocity seems to be the result of the buckets being about 2 feet above the aquarium. (Those closer to the water surface will probably not develop this high velocity.) Once set, this velocity will never change. The pump sending water to the aquarium will age and become less efficient. This will affect only the periodicity of the surge, not the discharge velocity.

All in all, I strongly encourage the hobbyist to experiment with devices of this sort. I can say they are much more efficient at producing water movement than a "dump bucket". And, in reef aquarium terms, these things are dirt cheap. And they don't take a long time to build either. In other words, there are few excuses for not trying one of these surge devices on your reef tank. If SPS (and other) corals were capable of emotion, they would love you for it.

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