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Aquarium.Net Nov 96 Building a Sand Bed System Aquarium

Sam Gamble Nov. installment on the how, whats and whys of sandbed sytsems,November 1996 Index for Aquarium Net, Aquarium Net has numerous articles written by the leading authors for the advanced aquarist

Building A Sand Bed System Aquarium

By Sam Gamble

So far we've gotten a baseline understanding of a sand bed system (SBS). The important basic concepts of what makes one work, and the generic appearance. Both of which are important when we actually get wet and dirty putting one together. The practical side.

To make this exercise modular and easy to apply to your particular design for bigger or smaller versions, I'll make the dimensions arbitrary and even numbers. The aquarium will be 100 gallons with the dimensions; length = 48 inches, width = 24 inches, with a height of 24 inches. It will actually be filled to 20 inches to get the desired 100 gallons. You mathematical and technical folks have already figured that out, eh?

Remembering with the generic example, the important components were a grid, screen, and sand layers. But, let's add some things to the materials list. This list is not exhaustive.

  • 3/4 in. pvc pipe cut into 2 in. pieces to be used as risers for the grid
  • sheet of egg crate used as the grid
  • enough pvc window screen to cover the grid (and the second layer of sand, optional)
  • about (6) 44 lbs. bags of aragonite sand with 1-2 mm grain size
  • 75 lbs. live sand for the top layer
  • dependable water pump rated about 2,000 GPH
  • strong lights, e.g. 3 (175 watt) metal halide 7K or 10K
  • 40 watt actinic blue fluorescent
  • two timers for the lights that are rated to handle the amps required
  • misc. pvc and plumbing supplies like primer, cement, teflon tape,m and pipe
  • numerous extra items that require unscheduled trips to the hardware store for unforeseen items that will connect from the pump to the aquarium and back again to the pump

To make the plenum,you install the grid. The grid is nothing more than "egg crate" which can be obtained at most hardware stores. It's what is used to diffuse light in ceiling fixtures. The screen is pvc window screen. Then you will need some pvc 3/4 inch pipe, and some tie wraps will make things easier. The size of the tank I chose, just so happens to fit a panel of egg crate (24 in . X 48 in.). Your tank may require cutting it to fit and using more pieces. Bottom line, make it fit snug. The objective is to keep sand and animals out of the plenum.

Cut the 3/4 inch pvc pipe into short sections about 2 inches long. Make enough of them to support the egg crate (grid), plus the weight of the sand and rocks. These are the risers laid on their side that produce the plenum space. The tie wraps can be used to secure the pvc risers to the grid. Secure the pvc risers and place all in the tank. Then cover the grid with the screen.

The screen must fit well, again, so as not to allow anything to get past into the plenum. Some folks go so far as to oversize the screen slightly and glue the edge to the side of the aquarium with silicon cement. Then you're ready for the first layer of sand.

Here is where a couple of tricks come in handy. Lets assume the grid and screen are in place and the pump and plumbing are ready for action (we'll get to the actual parts in a moment). Fill the aquarium enough to get the grid and first layer of sand wet. Now mix it around with your fingers to work out all the air trapped by the sand and particularly the grid. If you don't it will pocket air in the small squares, which will be a drawback for break in. Remember the purpose of the plenum and sand bed is to be anoxic ( DO around 2 mg/l) and subsequent facultative microbial populations. Pockets of trapped air won't help getting started.

Now that the first 2 inch layer of virgin aragonite sand has been built and worked, the second screen is cut to fit (optional). It may be hard to glue to the sides of the aquarium now that the first layer is wet and stirred around. The second idea is to oversize the screen enough so the next 1 1/2 inch layer will form a good divider from penetration when tucked down around the edge. Gluing can still be done, if you have the water low enough and prep the glass surface with alcohol to dry is satisfactorily for the glue. It's still going to be harder this time.

Top the second screen with 1 1/2 inch layer of more virgin aragonite sand. This will take the last three bags of sand. Again, it is advantageous to fill in more water and work it with your fingers to get some of the trapped air out. For the same reason as before.

Now we are ready to use the infamous live sand. Simply top the virgin sand with 1/2 to 1 inch of live sand and fill with water to cover. If the other accessories are ready, then the tank can be filled as per manufactures specifications (e.g. desired salt mix at about 1.023 specific gravity).

Accessories; which to describe first in this exercise, the sand bed or the pumps and lights, is like the "which came first the chicken or the egg". Most of the pump's plumbing and hardware, should actually be in place and ready before you splash the sand bed.

The pump(s) should be placed at midline relative to the water in the tank. In other words, at the middle of the tank. This will decrease the amount of work the pump has to do and will also keep it out of danger if there is a leak. Pumps that are placed on the floor have to develop more head pressure to get an equal amount of flow, e.g. turn over rate. When Murphy's Law goes into effect and a leak develops, a pump on the floor not only gets wet but presents an electrical shock safety hazard. A ground fault interrupter (GFI) is a very wise addition to the receptacle where you plan to plug in the pump and other accessories. A switch on that receptacle is also a wise feature for quick shut down situations. Who knows. Emergencies should NOT be shocking experiences.

Uptake and return plumbing will depend on the particular rig you devise and the space you have to do it. As well, the aquascape you've got in mind will determine what goes where. You may even get fancy and have special bulkhead holes drilled to facilitate this, without the pipes and overflow network going over the top. As for the particular options, go to aquarium club shows, or ask you friends, or ask your best dealers, or drop me an e.mail. There is some room for choice in this area. Bottom line it is best to keep it simple, straight line, and easy to work on. In the words of Henry David Thoreau, "simplify, simplify".

The lighting suggested is a simple version. For a tank of this size three metal halides will keep most cnidarians happy. There are instances where the ability to raise the light will be a handy feature. If the fixture is not an enclosed hood, you might include the ability to raise or lower the reflector with the lights. First of all being able to raise the lights out of the way will make working on the aquarium much easier come cleaning day. Also, there will be times when the amount of light can be adjusted. For example when a nutrient load is present, some corals do better with a temporary reduction of light intensity. Admittedly, that is a hard one to call.

The timers for the lighting should be set to roughly mimic a 10 -12 hour day. The actinic light is plugged into a separate timer to go on just before and after the bright lights. It's a nice natural touch. Not mandatory, however.

Other accessories like protein skimmers, refugia sumps, etc., may or may not be needed or desired. So I will spend little time in this area. I have seen successful systems with only a pump and correct lighting. In such systems the amount and circulation of flow relative to the aquascape is important. Bottom line, a sufficiently strong and thorough current is manifest to feed and cleanse the aquascape. This of course means a sizable flow across the top surface of the tank for gas exchange. Must note too, that a system of this type is delicately balanced to cycle controlled amounts of protein sources like food for fish. They do not make good mixed fish and invertebrate tanks, when considering a large biomass.

Let's assume then we are creating an environment aimed at a invertebrate community with just a few small fish to make it interesting. We have the lights and the pump running, so a few rocks in an aquascape wouldn't hurt. About 75 lbs. of the average cured rocks available on the open market are needed. The arrangement must provide for the previously mentioned circulation. This means over, under and through, if at all possible.

Remember nutrients have to reach the corals and wastes have to be taken from them, to areas where cycling can occur. As quick review, the oxic-anoxic interface and underlying anoxic filter bed have to be accessible at sufficient flow rates to achieve diffusion. Enough diffusion helps keep the equilibrium and energy cycles humming.

Equilibrium and balanced energy cycles are really what we are trying to achieve in our design and construction of this rig. Assuming that we now have the tank built filled and stocked with the basic aquascape, we need to monitor mother nature's reaction to our efforts. Early preliminary parameter measurements will flag some situations that need or do not need remedy. For example the rocks we added may contain more sources of organic compounds than expected. A lowered pH, low redox, and signs of ammonia or nitrite (however small) may give rise to the decision to keep the lights off or in the raised position. In extreme cases, do a water change.

In general we are going to monitor the tank for two things; 1. signs of organic compounds, 2. signs the microbial population in the sand bed is maturing and stratifying sufficiently. These two aspects will determine the rate at which we can proceed. If you can accurately say that the organic load is low and the microbial populations in the substrate is enough to handle the environment we just built, then it can be done all at once. It takes some experience and a little luck to build, splash, and stock, all at once. However, if it backfires, it's usually disastrous.

The upcoming section will continue with the activities after filling the aquarium. We will take it in steps and monitor important considerations while waiting for break in to signal the anticipated final stocking. In all too many cases, the anxious jumping the gun without adequate testing causes problems that haunt the reef keeper with continued problems associated to nutrient imbalance an unsynchronized energy cycling.

Next we will look at the procedures for avoidance.

Sam Gamble CompuServe 102170,3150

Created by liquid
Last modified 2006-11-20 04:02