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I don't like the look of powerheads in the aquarium. Hiding them behind rocks means they will inevitably fail, possibly frying your livestock and definitely forcing you to tear your reef apart to get to the powerheads. Also, like any submersible pump, the powerheads add the heat directly into the water; I have more than enough heat coming from lights, so I don't want any more.
The second circulation system is a closed system, drawing water directly from the tank and returning it to the tank, thus requiring no sump. Because there is no sump, there is no danger of siphon or water loss when the power goes out. I went this route because I can only run a certain amount of water through the overflow to the sump, and I wanted more circulation than that. Of course, all the pipes into and out of the aquarium have shut-off valves and unions, so I can remove the external plumbing to clean it out or fix leaks, etc. Catch the waveI started out knowing I wanted wave action of some type, for the benefit of everything in the aquarium. I figured I'd put both of the external pumps on an alternating wave system. I clearly wanted to use external, air-cooled pumps to avoid adding heat to the water. Unfortunately, turning electric pumps on and off all the time causes them to wear out pretty quickly because the motor undergoes the most stress during start-up. Also, if half your pumps are off and half are on at any given time, you need twice as many to provide the same amount of circulation! I have some large and fairly expensive pumps, so having them wear out or buying twice as many isn't an attractive proposition. I figured I'd use some type of automated valve to alternate the flow, so the pumps could run continuously and the flow would continuously change. Enter the three-way valveI spent more time than I wanted to learning about valves and figuring out what I could do. I looked at pneumatic valves, electrical valves, solenoid valves and ball valves. Finally I discovered what I wanted ;the three-way continuous flow automated ball valve. I chose valves from Hayward because of their outstanding reliability ratings and relatively low cost (they are still very expensive though!). They are surprisingly huge! In the picture below, the black actuator and gray valve together are well over a foot tall for the 1.5 inch PVC valve. (Note: on the Hayward web site you can find distributors of Hayward products in your area. I am not trying to push Hayward over other brands, but I have received a lot of emails asking for this info, so there you go!)
Here's some more detail into how this works; the left is with cover on, and the right is with the cover off the actuator so you can see the wiring.
For this reason, I wired the common to wire #1 in the actuator, and use the wave timer to do the switching between #2 and #3. (In the pictures of the actuator above, the wire numbers are shown in the gray plastic just above the white wire-connectors, with #1 on the far left). Don't be confused by colors of wire I used - in the picture above, the wires coming in the top are wires I connected. The wires coming in the bottom of the connectors correspond to the colors listed in the schematic. The AUX LIMIT SWITCH on wires 6,7, and 8 is an extra feature of the actuator that I don't use - I think it lets you control other devices with the same actuator. The wire I connected with the orange sheathing is white, black and green, but it is NOT the common, hot, and ground wires as the normal color convention for wiring would dictate. Instead, white is common, black is hot from wave timer channel 1, and green is hot from wave timer channel two. I wired the ground separately, which is not shown in the picture.
Of course I carefully planned the internal plumbing in the rocks so that the oscillations give interesting flow patterns, with sometimes opposing flows, and sometimes the same directions. After several months I accidentally broke the stop switches on one of the two valve actuators (I'm not sure how this happened), thus instead of turning around and stopping, it just keeps turning forever as long as there is power to the wire. Rather than pay to fix this, I came up with a flash of inspiration. I connected only one wire to the wave timer, and set the timer to have the power come on for about 10 seconds every 2 minutes or so. This means that every two minutes the valve rotates around for approximately 10 seconds (it varies) and stops at some random combination of flow to channel 1 and channel 2. Because I have a completely separate wave timer for the other valve I now get an infinite number of different combinations of flow. The two timers are moving the two motorized valves, one for the sump recirculation and the other for the closed system, at independent times and to an infinite number of possible flow patterns. This works beautifully. Since the actuators have a rated 25% duty cycle, for every 5 seconds they are "on" switching the valve, they need to be off resting for 15 seconds. This is no problem since I set my wave timers to change about every 2 minutes or so. Something to remember though so you don't burn out your actuators by turning them continuously. The drawback to this whole scheme is that the valves are 1.5 inch PVC, so they are REALLY expensive valves. The smaller valves are much cheaper, but these 1.5 inch valves with actuators and everything cost about $250 each. Of course, this is still less expensive than using twice as many pumps and turning them on and off, burning them up sooner. The actuators make some noise, but not much. Mine are drowned out by the pumps for sure! Hard to quantify noise in a useful way - I'd say they are maybe as loud as an HP laser printer while printing a page, and quieter than my electric pencil sharpener. Since the noise isn't constant, I would probably find it annoying if it were in my living room. Luckily, I have the noise-proof equipment room. Standing in the room, I can barely hear the actuators if I listen for them, since the pumps and skimmer and fans make MUCH more noise than the actuators. My corals love this setup. I noticed that when I had the wave system turned off for a couple weeks there was a BIG difference in the happiness of the coral. I am a real convert to a wave system, which I didn't have in my previous tank.
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I wanted to have
two separate circulation systems, both on external air-cooled pumps. I chose
Dolphin 3 pumps, rated at 3600 GPH. I chose these for their reliability, as well
as low cost and low power consumption for the amount of water moved. One pump
would return the water from the sump to the aquarium, going over the top edge
and down into the aquarium, where water would be dispersed via pipes hidden in
the rock. You can see and read about the pipes under the rock on the 
But this
drawback is well worth the certainty of preventing the whole tank from siphoning
down the floor drain when the power goes out. Of course the sump is sized to
hold all the water that drains back before the siphon breaks when the power goes
out. There are actually 4 pipes going over the edge of the aquarium, and I
wanted water flowing through 2 of them at a time; the wave system would trade
back and forth between the two pair of pipes as a sinusoidal oscillation.
The three-way valve
means that water enters the bottom, and goes out either to the right or the
left, depending on the valve position. Continuous flow means that the two
channels are NOT mutually exclusive; that is, as you turn the valve, flow
decreases in channel 1 at the same time it increases in channel 2, until you
finally have flow from only one channel. This is beneficial because while the
valve is changing, there is no back-pressure on the pump, which causes motor
stress, more heat, and possible cavitation (lots of bubbles in the water).
Continuous flow keeps the water moving, with the flow smoothly increasing or
decreasing over about 5 seconds as the valve changes. 
The actuator, or motor,
is model EA2 from Hayward. Nothing special, its just the cheapest actuator that
went with the 1.5 inch 3-way FULL-FLO ball valve. It works by having two different 110Volt AC
circuits. You give power to one and the
valves turns around to channel 1 and stops. Power the other and the valve turns
to channel 2 and stops. It takes around 5 seconds to change positions. I chose this type because I can use it with a
simple wave-timer to alternate power to the two wires every few minutes,
smoothly changing the flow back and forth. Imagine two out-of-phase sine waves. Presto! Works like a charm!
The actuator
schematic shown at right indicates that white wire #1 should be common, and
black and brown are switched between input wire 2 and 3, so one or the other has
a circuit, but not both. It turns out that powering both at once doesn't damage
anything, it just makes the valve keep turning forever. I used a voltmeter to
check my wave timers - it turns out that with the wave timer I use (Natural
Wave) the neutral, or common wire (usually the white wire in the U.S. wiring
standard) is constantly connected, and the wave timer simply turns the
"hot" wire on and off. Since this is the reasonable way to build a
wave timer, I'm sure most other wave timers work the same way. Luckily this is
just what the valve actuator needs!
Here you see the plugs
into the wave timer. I used a pen to mark the wave pattern on the wave timer.
Since channel 1 and 2 of the wave timer are inverse patterns, I connected white
wire to the neutral wire of both #1 and #2, and used green to get the hot from
channel 1, and the black (hidden behind the sheathing) to get the hot from
channel 2. This lets me use the three-wire orange sheathed wire from an
extension cord, which I had laying around.
