With this final installment in this series of articles on Aquarium Water Pumps, I will discuss some of the techniques and methods for installing pumps, and in the process describe some of the different uses these pumps can be put to in aquarium systems. I will try to simplify things at the start by categorizing most pump installations as being one of three types:

Internal Only - All pumps are internal to tank(s). Generally, power heads or other submersible pumps.
External Only - All pumps are external to tank(s). May be a submersible or non-submersible stand alone unit, as well as part of a filter such as a canister or hang on back of tank unit.
Combination - Both internal and external pumps.

Each of these configurations can have numerous variations, and I will try to point out some of these, where appropriate, and discuss their relative merits.

When you are preparing to install a water pump in an aquarium system, there are various factors that will be influencing the final configuration. Among these factors are available space, tank heating, noise level, performance requirements, maintenance, reliability and safety. I will discuss each of these and offer some examples as to how they may be attended.

Example #1: Internal Only System.

There are probably three primary variantions of this system, and Figure #1 shows two of these that use power heads to provide circulation, either with or without an undergravel filter. The third type of popular internal system would be one that has filter chambers built into the tank itself. The advantages to internal systems of this sort should be obvious; little additional plumbing is required, and the size of the pumps can be smaller for any given flow rate, since they have little or no elevation to pump against. Undergravel filters do cause pumping losses due to having to suck (or push for reverse flow) water through the gravel/sand bed. Some of the disadvantages to using internal pumps are: valuable tank space is used for pumps and filters, large amounts of potentially unwanted heat will be dumped into the tank, and the types of filters that may be used is more limited.

With the exception of the undergravel filter, where the placement of pumps is dictated by the filter itself, the challenge in placing internal pumps is in finding a location that provides good circulation and is visually inconspicuous. The placement should also allow easy access for maintenance, if necessary (No hiding pumps under reef rocks!) My personal preference is to locate these internal pumps near the tank's surface on the sides or along the back to encourage good gas exchange (high oxygen levels in the water) as well as increased evaporation in an open top tank. The latter benefit may seem strange to some, but can be extremely useful to a reef tank with a high intensity lighting system that is transferring significant amounts of heat to the tank. Evaporation in the tank removes heat (it's how an air conditioner or chiller works), and thus helps to cool the tank. Another side benefit of causing surface disturbance with pumps when using metal halides is the aesthetic shimmering effect created by the lighting that I think makes for a visually more pleasing effect (this effect is very limited with fluorescent lighting systems). From a visual perspective, if you place the pump(s) in the back of the tank in an upper corner, or mount it under the tank lip in conjuction with a canopy or other tank cover, the pumps will be hardly noticeable. As coralline algae grows on them, they will eventually look like a natural part of the tank.

If you do not have a stand pipe, as with an undergravel filter to place the pump on, how do you most effectively mount it in the tank? You could use the suction cup mounts that come with many of the power heads, but I find these unreliable as they have a tendency to come loose after a while. If you have a glass tank, then the hang-on mounts that also come with many pumps may work fine, but these will not work well with acrylic tanks. You can glue the pump mounts to the tank, but this reduces the flexibility in adjusting or moving the pump to meet different requirements. Figure #2 shows a couple of suggestions for mounting internal circulation pumps near the surface in acrylic tanks.

Another issue with internal circulation pumps is what to do about the inflow to the pump. If you have larger fish in the tank, then you can probably just leave the inlet uncovered, as it is unlikely that fish will be sucked into it. On the other hand, if you have smaller fish or invertebrates in the tank, then you need to be worried about these animals getting sucked into the pump's impeller and being injured or killed. Some internal pumps come with a screen or a filter that can be placed on the pump's inlet. The filters work, but require periodic cleaning or the flow rate of the pump will gradually be reduced as the filter gets clogged. Some of these filters may be as large or larger than the pump itself, so you have to provide space for them and, of course, they will be more conspicuous. In a pinch, you can often take a piece of nylon screen, double it and place it over the inlet, attaching it with a cable tie or fishing line.

Example #2: External Only System.

Figure #3 External pump example

Figure #3 shows a fairly common sump/tank configuration that uses an external pump. The pump shown in the Figure #3 is non-submersible, but as long as there is sufficient space in the sump, a submersible pump could also be used. I've included an internal box overflow in the tank for this example as they are fairly common and quite useful. If an external canister filter is used, then an overflow may not be needed, although they are still very useful for skimming the tank's surface. Once the pump(s) is located external to the tank, the plumbing requirements become more complex.

Unless a submersible pump is used (see Parts 1 & 2 in this series to help determine which type is best for your application), there must be some way of getting water from the sump to the pump. This is normally accomplished through the use of a bulkhead fitting which attaches to the sump through a hole drilled into it for this purpose. The bulkhead fitting allows the attachment of pipe or tubing to the sump which can, in turn, be connected to the pump's inlet. Theoretically, a siphon could be used to connect the pump to the sump, but I find siphons, unless part of a closed canister filter system, to be very unreliable. They are often difficult to start and I do not recommend them. Another recommendation is that the bulkhead fitting be located as low in the sump as possible, and an elbow fitting used to lower its input to just above the sump's bottom. This low inlet to the pump helps in several ways: first, it allows the pump to operate until the sump is nearly empty; second, it also keeps larger objects from getting sucked into the pump (you could also use a pre-filter but that requires periodic cleaning) and third, it makes it easier to prime the pump. Priming the pump refers to filling its inlet and wetted portions of the pump with water; this is necessary in most centrifugal pumps to start them pumping. Very few aquarium pumps are self-priming or able to suck water into their inlet, unless they have water in them prior to applying power to the pump; locating the inlet of the pump below the water level in the sump provides an easy way of automatically priming the pump via gravity flow.

I have also showed the control valve on the outlet of the pump in Figure #3 in a position to adjust its flow rate. The inlet service valve could also be used to control the pump's output, but most pump manufacturers recommend against this practice. With powerful pumps and/or too much throttling of the flow, cavitation may occur in the pump, thereby harming it. One reason for placing a valve on the inlet side of the pump (service valve in this example) is that this valve, in conjuction with a union, will allow me to remove the pump for maintenance without having to drain the sump. The unions are the fittings located between the pump and the valves (see Plumbing 101 for additional information) and allow the disconnection of the pump by unscrewing the union, after first having closed the valves to prevent water loss from the sump and tank (there will still be some mess from the water in the pump, but it can normally be managed with minimum effort). Most pumps require very little maintenance, but should be taken apart for cleaning at least once a year to make sure they continue to operate at peak efficiency. Additionally, some pumps require periodic oiling of certain parts (check with the manual supplied with the pump). As I've often said in the past, maintenance of this sort will usually only get done if the work required is minimal, and a plumbing configuration as described above will make this job a lot easier.

While I have mentioned connecting the pump to the sump, I have not yet said anything about where the pump is placed, or how it is mounted, besides the requirement that the pump's inlet be placed below the sump's water level to help prime the pump. The most common arrangement for a pump in this type of configuration is to place it adjacent to the sump on the same support surface. There are a couple of reasons that you may wish to modify this configuration slightly by elevating the pump from the sump's support surface. A non-submersible pump is called that for the simple reason that it will be damaged if water gets into its motor, or if its case is subjected to prolonged contact with water (especially saltwater). As most surfaces around a sump are subject to occasional splashes or overflows, it is a good idea to minimize the amount of moisture to which the pump is exposed by slightly elevating the pump (generally 1/2" is sufficient) above the sump support surface. Another good reason for elevating the pump is to reduce the noise of the pump's operation.

Pumps, by their very nature, make noise, mainly through vibration of their housings due to the rotating components. While some of this noise is transmitted directly to the air, it is often the case that much of this noise is caused by transmitting vibrations to other surfaces, such as the floor that the pump is placed upon. This noise may be significantly reduced if the pump can be acoustically isolated from the mounting surface. Acoustically isolating the pump reduces its vibrations by dampening or deadening them before they are transmitted to the floor or other mounting surface. The best way of accomplishing this is to use a piece of 1/2" thick rubber mat between the pump and the mounting surface. The mat will provide good support while helping to dampen the vibrations of the pump. I've also been told that indoor/outdoor carpet will work well. Whatever material you use for a pump mat, it must do three things: provide adequate mechanical support, dampen mechanical vibration and not be damaged when it gets wet.

I have assumed so far that only rigid pipe has been used, and while flexible tubing could be used, it is normally better to use rigid pipe to help support the inlet valve and to make it easier to adjust. On the outlet side of the pump (or the outlet union if you are using one), you may use either rigid pipe or tubing. If you have to support additional filter stages between the pump and the tank, then rigid pipe is preferable for the added support it provides. Alternately, if you need to route the plumbing to the tank through twists and turns, then flexible tubing offers many advantages. These include the ability to make more gradual turns, creating lower pump losses (see Part 2 of this series), which, in turn, results in higher available flow rates from a given pump. Do not be afraid to mix both pipe and tubing where appropriate. Some words of caution: as the tubing diameter increases (>1"), its flexibility decreases, thereby reducing its advantage unless long runs are planned (where limited flexibility may still help).

The final example I wish to discuss is the return to the tank itself. Notice that in this example (Figure #3) the return is located at the surface of the tank. The return could be extended to go to the tank's bottom (shown in dashed lines), but there are potential problems in doing this. If the return is below the surface of the tank and the power is shut off, then the return will act like a siphon, and the tank will drain into the sump until the level in the tank is below the return's end, possibly draining the entire tank. This problem may be avoided problem in a couple of ways: by either using check valves in the return lines or by placing a siphon break in the return near the surface of the tank. If you use a check valve (a check valve only allows water to flow in one direction), position it so you can easily remove it to periodically clean it as it can get dirty from debris or internal growths that could prevent it from working properly. My favorite position for a check valve, if there is adequate space, is inside the sump on the incoming side of the bulkhead fitting (see Figure #3). A siphon break is nothing more than a small hole drilled in the return near the surface of the water (see Figure #3). When the power is shut off, the hole allows air from the surface to be sucked into the return and breaks the potential siphon. A word of advice - it is very wise to do a power cycle check on any aquarium system. This means shutting the power off for a short period of time and making sure nothing unusual happens (e.g. tank draining, sump overflowing, etc.) You can then turn the power back on to see if all the pumps, filters, overflows, etc. start properly.

Example #3: Combination System.

Figure #4 Combination external/internal pumps example

This is my preferred aquarium configuration for all but smaller systems or specialty situations, and involves the use of both external and internal circulation pumps for added reliability. The configuration shown in Figure #4, is similar to Example #2, but has additional internal circulation pumps to supplement the single external pump. For even better reliability, or with a larger system, I recommend multiple external pumps as well. When using internal pumps the external pump(s) can be reduced in size (along with noise, cost, and power usage), since not all of the circulation requirements need be supported by a single pump. You also have more flexibility in supplying good circulation to the whole tank since there are multiple outlets directing the water. You may split a single pump's return and get a similar effect, but without the improved reliability and added protection acheived by using multiple pumps.

You may potentially improve the circulation in the tank even further if the internal pumps are placed on timers, or if a wavemaker is used to alternate or randomize the outputs of these pumps. This cycling of the pumps helps prevent stationary circulation patterns in the tank and thus better circulates all areas. Water constantly flowing in the same direction can be especially bad for some corals or invertebrates, as only one side or area of the specimen will receive good circulation. Make sure that any timer or wavemaker used to control the pumps is properly sized for the pumps you are using (i.e., can handle the current requirements of the pumps) and that the pumps being used can be reliably turned off and on repeatedly by the wavemaker/switch being used.

Notice that the return to the tank in this example is split at the output of the external pump into two separate returns. While more complicated, this can be very useful to reduce possible pump flow rate losses, especially if a long run is required from the pump to the tank. As mentioned in Part 2 of this series, a pump's flow rate losses due to plumbing are greatly dependent on the velocity of the water in the plumbing. By splitting the tank return into two separate returns, you reduce the output velocity in half and achieve significantly lower pump losses. You could alternately use a larger diameter pipe/tubing for a similar effect, but having multiple returns to the tank gives added flexibility in locating returns in the tank to get the best circulation patterns.

In Parts 1 and 2 of this series on water pumps, I strongly suggested that when using electrical equipment around water, it is best to use Ground Fault Interrupter (GFI) equipped electrical circuits to prevent electrical shorts from becoming dangerous to either you or the tank. When a GFI detects a short has occurred, it shuts the offending circuit off. One possible danger to using a GFI circuit is that if all of a tank's electrical equipment is connected to a single GFI, then they will all be shut off until the short is fixed and the GFI is reset. Having the whole tank shut off due to one pump or other piece of equipment having problems is not desirable. Ideally, there should be one GFI for each piece of equipment; the use of multiple GFI circuits for different pumps will maintain the tank's circulation in the event of a problem and reduce the risk of a total shut-down. Strategically grouping your equipment, so that if any one GFI trips it will not seriously endanger the tank, is a wise course of action.

Another desirable electrical redundancy, especially in larger systems, is to split equipment so that it is divided between two or more separate electrical circuits. A separate electrical circuit is defined by having its own fuse or circuit breaker at the main power box. This allows at least part of the tank to continue running even if a breaker or fuse is tripped due to overloading or other potential electrical failure. Again, you need to strategically group the various pieces of equipment between the different circuits so that the loss of any single circuit will not cause the entire tank to fail.

This concludes my series on aquarium water pumps. I hope I've given you a basic understanding of how these pumps work (Part 1), how to go about choosing a pump for a given application (Part 2) and, finally, some suggestions of how to install your pumps to get the maximum performance and reliability out of them (Part 3). Obviously, you can have any number of variantions on the pump configurations mentioned, as well as some I did not cover (in particular, use of metering or dosing pumps). Don't be afraid to experiment and use some of the principles covered in this series to optimize your tank(s) circulation for your particular requirements. If you have a particularly clever or different way of using pumps for circulation or other aquarium applications, let me know what they are, and I'll try to include them in a future update to this series.

If you have any questions about this article, please visit my author forum on Reef Central.

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Aquarium Water Pumps: Operation, Selection and Installation: Part 3 by Rex Niedermeyer - Reefkeeping.com