Are Rotating Powerheads Any Good?

There are several important factors that should be present if a marine aquarium is to be a success. In both fish only and reef aquariums seawater movement is one of them.

One reason for the importance of movement is oxygen intake, if it is adequate the seawater will constantly reach air/water interfaces, in particular the display aquarium surface, where gas exchange can take place. Another reason is that it assists corals obtain food and rid themselves of mucus.

There are several ways of providing adequate movement, some advanced and some ‘basic’. It is likely that many (most?) aquarists use ‘basic’ equipment, namely powerheads. These devices are available in more than one type, though they are all basically an electric motor made seawater safe by encapsulating it in resin, the motor drives an impellor, and there is a seawater intake and outlet. The powerheads could be narrow outlet or wide (‘soft’) outlet types. The wide outlet ones are able to move large quantities of seawater but because they push out the seawater on a wide front the impact is soft and not harmful to corals, particularly if there are two in opposition or they are timed. Narrow outlet powerheads pump a much thinner stream of seawater which is very linear and can damage fairly close corals because of the force.

Random and chaotic seawater movement is the aim and this is often obtained by placing powerheads in opposition to each other and also ‘bouncing’ the outlets off the glass. This should result in the desired seawater flow once a bit of trial and error with powerhead positioning has been completed.

With the narrow outlet powerheads there is a further option and this is to use the generated flow of the seawater to drive a mobile directional outlet. This type of outlet can be bought as an ‘add on’ or alternatively a powerhead obtained which has the required outlet fitted. What happens is that the flow of the seawater from the powerhead causes the outlet to swivel from side to side in an arc. The movement of the outlet is not particularly fast and when the end of the arc is reached the direction is reversed. Another method is an outlet that spins, the seawater acting something like jet propulsion driving it round.

This idea has merits. The seawater flow is automatically being re-directed continuously which is good and in itself is going to create varying currents in the aquarium. If there are two powerheads present, for example, and each has a rotation ability then continuously varying seawater flow will be generated at each end of the aquarium. In addition, from time to time the outlets will come into direct opposition to each other and create more random currents.

Of course there have to be disadvantages! First of all, the rotation is driven by the outlet from the powerhead which detracts from the strength of the flow, though this could be compensated for by the powerhead strength itself. The rotation mechanism is submerged in seawater and there is the possibility (probability?) that the rotation will slow down or cease because of calcareous build up. Also, the seawater from the outlet is still linear even though it is rotating, though it would hit a coral that is in the way X number of times per minute rather than continuously. Standard powerheads require their outlet strength checking from time to time and in addition the rotating powerhead needs checking to ensure the rotation mechanism is operating correctly, meaning there is a small addition to routine maintenance checks.

Rotating powerheads are a useful idea and I have nothing against them. However, and this is purely personal, I prefer standard powerheads that have been correctly sized and placed. Better in a suitable aquarium would be wide or ‘soft’ outlet powerheads in opposition, or timed.

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Closed Loop Water Circulation

As with many things in this hobby closed loop circulation is a subject matter which can be quite confusing. This topic has been briefly covered before however in this article I hope to cover this area in more detail.

Water circulation in an aquarium, especially a reef aquarium where closed loop circulation is more suited for is exceptionally beneficial. I rate water circulation as third in a list of must haves – the two above it are water quality and lighting. Water circulation by many is actually classed within the water quality area however I prefer to keep it separate.

Water circulation within a reef aquarium is important for many reasons. It allows for food to be provided to corals, waste to be removed from corals, oxygenation of the water at the air interface, delivery of water to live rock as well as making the aquarium a more natural habitat for the aquarium inhabitants.

There are many ways for the aquarists to provide water circulation of which the closed loop method is just one.

So what is closed loop circulation, what are the benefits and how does it work?

The easiest way to describe closed loop is using an external canister filter as an example. With an external canister file there is in inlet pipe which delivers water to the filter. The canister filter pump then pushes the water through the filter and it is delivered back to the aquarium via a single outlet.

Closed loop circulation is exactly the same as this with the exceptions that there is no filtration involved and that the water velocity is greater.

Sounds very simple and in reality it is. With a closed loop the water inlet to the pump (which is located externally to the aquarium) is located underwater as is the outlet so effectively you have a ‘closed loop’ of pipe work which is connected to an external pump.

The inlet, pump and outlet when connected together are known as a loop

What happens is that water flows down the inlet to the water pump. When the pump is switched on water is forced up the outlet pipe and out into the aquarium. With water being pushed up the pipe water is drawn down the inlet pipe and the cycle continues.

In this type of system normally one pump is used per loop however one loop can contain numerous outlets. For example the inlet is under water in the aquarium. Water is provided to the pump which, when turned on pushed water back up into the aquarium. As the pumps output is connected to pipe work this is run up to the aquarium and then inside the aquarium. Once in the aquarium there is a run of pipe which can be located anywhere in the aquarium as long as the outlet(s) are under water. It is normally recommended that a loop has no more than 3 outlets however it does need to be noted that the more outlets the loop has the more the power of the water force will reduce. Therefore from one loop you could have three outlets which can be located in different areas of the aquarium, therefore providing more areas of flow from one pump.

So why would anyone consider using more than one loop? This depends realistically upon the size of the aquarium and types of corals being kept in the aquarium. If you keep short polyp stony (SPS) corals then these require stronger water circulation therefore with no closed loop devices you will either require stronger devices or more of them.

The other consideration is the physical size of the aquarium. The bigger the aquarium the more water there is and therefore more water to move around.  As with the above example in relation to SPS corals you can therefore either purchase more devices or purchase more powerful ones.

With more than one loop in the aquarium you can provide more outlets to where it is required most. For example if you have a 4*2*2 aquarium which is stocked with SPS corals then you could use stream like devices which do create excellent water circulation however these would be visible within the aquarium or you could create some loops.

In the above example what you could do with a closed loop system is install two loops. Both of these loops would have their dedicated inlet as well as a dedicated pump however you could feasibly have up to six outlets.  Once the pipe work is plumbed back from the pump to the aquarium these could be located in numerous areas of the aquarium. You could have two outlets at the corners in the front bottom of the aquarium pushing water up the rock face, another two could be in the rear upper corner and another couple could be hidden in the rock face. All the pipe work could be hidden from view either within/behind the rockwork or under the sand. All that would be visible would be the outlets and these would become covered in coralline very quickly.

The water flow created by a properly designed closed loop system can be fantastic however there is some planning to do.

The first thing you need to consider is the physical power of the pump. The pumps are rated at zero head height with only one outlet. If you only plan on using this outlet then this will be the output you can expect from the pump. There is no head height restrictions in a closed loop system but I will go over that shortly.

The second thing to plan for is the amount of outlets per loop. It is recommended that you do not go above three outlets per loop as the reduction in flow may be too much. Pumps are rated in accordance with the size of the outlet coming out of the pump and with a pump there is only one outlet. If you put three outlets onto a closed loop then effectively the output from the pump per outlet will reduce. Normally in a loop this reduction is staged with the last outlet having the weakest route – I will cover why this is shortly.

The location of outlets is an important thing to plan for. You don’t want to install your rocks and then plumb around them. It is much easier to attempt to design where you would like the outlets to be. Of course when you aquascape the aquarium this design may have to change a little however it should not need to change that much.

The physical plumbing is also an area which requires consideration. With a closed loop system you will have one pipe for the inlet and another for the outlet. With this plumbing running down to where the pump is located there may be a fair few pipe, especially if you install more than one loop! The run of these pipes will need to be roughly planned for and it is wise to ensure that they are located in an area where they are accessible. If a leak was to occur then you want to be able to get to the pipe work to rectify the issue.

Plumbing is an important aspect to this as there are many ways to ‘plumb in’ a loop. The connections to the pump are fairly straight forward. Either the pipe will attach directly to the inlet/outlet area of the pump or if not you simply attach some flexible tubing to the inlet/outlet, heat up the other end and stretch it over the pipe using bushes if required. It is the inlet and outlet which is important. There are effectively two ways in which the inlet and outlet can be integrated with the aquarium. The first is that the pipe work goes up and over the aquarium edge. Effectively pipe work is run up the exterior of the aquarium and then using bends it is taken over the edge and into the aquarium. On the inlet it is best to implement some type of protective cover to prevent livestock etc being drawn into the pump. The outlet is simply taken over into the aquarium and the outlets plumbed in.

The other way to achieve this is to physically drill holes in the aquarium. One of these would be for the inlet (again covered with a protective covering). In this hole would be a tank connector which the pipe work would be attached to and connected down to the pump. The outlets could either be just the one hole of one for each required outlet. With one hole you could just use it as a single outlet or you could plumb pipe work internally to more outlets. With more than one drilled hole you can split the pipe externally to the aquarium and deliver one pipe to each hole. With all holes you will need to install a tank connector and then connect the pipe to this.

Plumbing the loop(s) in is quite a simple process. It has been briefly covered above how to attach the pipe work to the pump however one area which I would recommend is locating the pump on some sort of media/device which will absorb vibrations. The pump, due to it having moving components is going to vibrate and due to hard pipes being attached to it may sometimes cause noise. If you locate it on some media then this noise will reduce. I have had numerous closed loops and have not been able to hear the noise of the pump. Due to vibration I personally prefer to attach flexible tubing to the pump and then attach the hard pipe to the flexible tube. This method therefore allows for a certain amount of give.

Take your time when plumbing the aquarium. As the old saying goes ‘measure twice and cut once’. You need to ensure that the pipe work you purchase is of food grade quality. Fortunately most quality online and offline shops now stock various types of plumbing components. You will also need some ‘glue’ for connecting the pipes together – this is not just normal household glue it is special glue which again you can get from your local fish shop or reputable do it yourself store.

When you cut the pipe always ensure that the ends have a straight cut. Once the cut is made ensure that any loose areas are moved and/or cleaned and then de-burr the end. You will require connectors to attach the pipes together. Considerations into these are given later. I would recommend not rushing this point and always dry test each pipe/connector. Once you are happy with the connection glue them together. Once the glue is set the only way you are going to be able to get them apart again is by cutting them!

Once everything is in place the next step is to get water into the pipes and all the air removed. If you have drilled holes in the aquarium for the inlet/outlet(s)s then water will already be in the pipe and as soon as the pump is activated any remaining air should be pushed out. To check if there is any remaining in the pump simply rock the pump gently to remove any trapped air bubbles.

If the loops are configured in an up and over fashion then this is slightly trickier to accomplish as the water has not ability of getting up and over the aquarium edge. There are a few options available to accomplish this task though.

The first one is by simply sticking some air line up the inlet pipe so it is as high as it will go and then sucking the air out until you effectively get a mouthful of water. When the pump is turned on any remaining air should be blown out of the outlet. If you choose this option then I would recommend putting a gang valve onto the air line so that you can have a break.

The second one is by drilling a hole in the very top area of the pipe where it goes over the aquarium edge. Into this hole insert some tubing and seal it in place using sealant. It is imperative that a very good seal is made as you do not want any air to get into the tube. Install a gang valve onto the airline and then suck out the air. Once you get a mouthful of water close the gang valve. When the pump is turned on the water will flow however this will create pressure on the gang valve therefore I would recommend that you bend this over into the aquarium and open the gang valve. As the pump is running a small amount of water will flow out of the airline tube into the aquarium.

That’s how closed loop plumbing effectively works however what are the benefits and are there any other considerations?

Before the considerations let’s have a brief look at the benefits of closed loop circulation.

The main benefit is the actual water movement which is created in the aquarium. Due to the large outlets which can be used and the powerful pumps which can be implemented the flow is very powerful however it is also very wide and soft. This is much more beneficial for corals as they require a lot of water movement but they do not want/like water movement which is forceful, in actual fact it can damage them sometimes even tearing the coral away from its skeleton.

Another benefit is that a very un-natural looking device is removed from the aquarium. Power heads etc are very good devices at moving water around however they are, in my opinion, quite intrusive. With a closed loop system the physical device is removed from the aquarium, out of view with only the outlets being visible.

With the pumps being external to the aquarium a heat source is removed from the aquarium. Whilst this heat source may be valuable during the colder months it is certainly an issue during the warmer months. With the heat creating source being physically removed it can, at times be easier to provide stability in relation to temperature.

A very valuable benefit of a closed loop system is that there are no head height restrictions. The rating of the pump is what you should get – even if the pump is three feet lower than the display aquarium. Head height is effectively due to gravity where the water when rising up a tube has to fight against this natural force. The pump can only pump the water so high and then simply runs out of power. If a pump has a four foot head height then at four foot above the pump the water flow will stop, at two foot above the pump the flow will be halved etc. With a closed loop aquarium head height does not exist. The reason for this is that the water does not have to fight against gravity as no air is allowed into the pipe work. The inlet pipe is continuously full of water as is the outlet therefore with no gravity to fight against you get full use of the power of the pump!

The above is the main benefits now let’s move onto some considerations.

The first consideration is that of water flow and friction. Water will always find the easiest route and follow it which is one of the reasons you need to plan your plumbing. If you implement a tee piece for example the water in the pipe will travel down the easiest route and therefore water flow down the secondary path may be severely impacted. Friction is also the same – although the inside of the pipe feels smooth to the touch it will create friction when in contact with the pipe. When in a straight line this friction is not a problem however bends are another kettle of fish altogether. If you need to go around a bend it is easy to install a 90 degree bend however this is quite a bend for the water to go around and the flow will be severely impacted as well as creating back pressure within the pipe which over time may damage the pump itself. If you need to go around a corner then it is better to use two 45 degree bends instead of a single 90 degree bend. Even better is to use rigid pipe which  is slightly flexible which will allow you to create a gentle curve around corners.

When the plumbing is complete and all the outlets are in place it is highly recommended that you perform a dry run. This is probably not the best name for it as water is involved but what I mean is that you fill the aquarium with household water and then test the loops. If you locate a leak then you can lower/drain the water and rectify the problem. If you fill the aquarium with reverse osmosis water, add salt, test and identify a problem then this is a waste of reverse osmosis water and salt – both of which are expensive.

All devices at some point will require maintenance or may even fail altogether. With a closed loop system the pipes are continuously full of water so if you remove the pump then you may get a wet floor as the water continues to flow through the inlet. I would recommend that ball valves are installed into both the inlet pipe and the outlet pipe. Should you need to remove the pump for whatever reason then you simply need to close the ball valves prior to removal. Once the pump is reinstalled the valves can be re-opened plus you won’t need to re-prime the loop!

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Why The Emphasis On Seawater Movement?

Seawater quality is a high priority in a marine system, and without it the aquarist is going to have niggles and problems. Maintaining seawater quality nowadays is easier with all the technical support equipment available, for example the protein skimmer and the high quality dry salt mixes that are commercially produced.

Even with seawater mixed properly and equipment fitted correctly, the quality story doesn’t end there. There is another important requirement and that is adequate seawater movement. Without this the aquarist will still likely be faced with niggles and problems. It could be argued that movement is a part of seawater quality as it contributes to it so significantly.

Before going further a mention of the guidelines for movement should be made. Note that these are guidelines and not rules. They provide a basis which could be altered if the need arose. In a fish only aquarium seawater movement should be around 10 times the net gallonage in the display aquarium. In a soft coral system the same guideline applies. In a hard coral (SPS) system the movement should be around 20 times the net gallonage in the display aquarium. Note that these guidelines are for the display aquarium only, if a sump is used this is not included in the gallonage calculation.

With adequate movement any temperature differentials will be minimized, and the heater’s controlling thermostat will more likely read the average temperature and react correctly. A temperature differential could occur for example in an area where there is very sluggish movement as the seawater enters and exits the area very slowly. If there is adequate seawater movement overall then as said the heater thermostat will read the overall temperature more correctly. There are always areas in a system where the seawater flow is lower, for example in and under reef rockwork or in the corners of the aquarium. It is sluggish flow that needs to be avoided.

Fish will be healthy and more settled, all things being equal, where there is good movement. It is reported that in sluggish or still seawater fish could be surrounded by a thin ‘dead’ area that interferes with their osmosis needs. In any case, on the wild reef the seawater isn’t usually sluggish and life adapts to its normal environment over a long period of time.

Where there is a reef with soft and/or hard corals, movement is very important. Corals rely on movement to bring food to them, and at the same time remove mucus and dirt. Coral extension should be better with adequate movement and, again all things being equal, growth and colour should be good.

The following is probably the most important aspect of ensuring that seawater movement is as it should be. There is an ongoing requirement in a marine system for stability and there should be nothing that could affect this.

Gas exchange is often mentioned in relation to marine systems, and this simply means the exchange of gases at air/water interfaces. Unwanted gas escapes and another, oxygen, is taken in. Air/water interfaces are the seawater surface in the display aquarium and also in the sump if one is used which are the most important, and also seawater flowing over weirs and down overflow pipes. Some equipment presents an air/water interface, for example the protein skimmer.

If there is to be adequate gas exchange it follows that the seawater must continually move to the surface and away again. Where movement is adequate this happens and the seawater from all parts of the aquarium meets an air/water interface. Movement is often more vigorous in the upper areas of the aquarium but this doesn’t matter provided the lower areas are moved reasonably also.

Everyone knows that life forms require oxygen, including humans. Fish etc have less available to breathe than humans – there is about twenty times more in the air than there is in warm seawater. Cold fresh water holds more oxygen than warm fresh water, and warm fresh water holds more than cold seawater. As the seawater temperature increases, so there is less oxygen. In a reef aquarium that is well designed and maintained the oxygen content is around 6 to 8 ppm (yes, that’s right, about 6 to 8 parts per million! Not a great deal). The fish and other life have a constant demand for oxygen and so it must be constantly replenished or, particularly in a heavily stocked fish only aquarium, there will be problems. An example of how a dangerous state can arise with oxygen levels is where a lengthy power cut occurs and all seawater movement has stopped. The fish etc continue to breathe of course, and eventually the oxygen content of the seawater drops very low. The fish will eventually probably come to the surface and gasp as there is some remaining oxygen in that area, they might even extend their mouths above the surface in a desperate attempt to breathe. If the seawater circulation returns in time the situation will remedy itself and all should return to normal.

Good seawater movement is going to provide adequate oxygen, which will be moved to all areas of the aquarium ensuring that all life has a supply. One very essential area that needs the oxygen is the bio-filter. Those hardworking friends of the aquarist, the bacteria, are oxygen hungry and must have an adequate supply to function (those that convert the toxins anyway).

Talking of bacteria and bio-filters, aquarists using live rock have the advantage that the whole of the nitrogen cycle should be achieved, which are the conversion of toxins and the reduction of nitrate. When the bacteria remove oxygen from the nitrate so breaking the nitrate down, the result is released as gaseous nitrogen. It is released at air/water interfaces so again circulation is important.

There isn’t any intention of delving into chemistry as there isn’t a need here, but seawater could be adversely affected if there is poor circulation – as gases cannot easily be released from the seawater pressure increases for the seawater to react in an unwanted way. There could be a reduction in pH for example. Stability is required and good seawater movement goes a long way to provide it.

Creating seawater movement is straightforward and could only need for example two powerheads, though the need will vary from system to system. Linear seawater movement is not required and a little experimentation with positioning the powerheads should produce chaotic or more random movement, which is required. Whatever method to move the seawater is used, the livestock will demonstrate their appreciation with better health and colour.

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One Return Pump Or Two?

What is a return pump? These pumps are used for returning seawater from a sump to the display aquarium. They are used in fish only aquariums and reef aquariums, provided the system includes a sump of course.

Equipment nowadays is generally very reliable and many aquarists don’t back-up anything. Fair enough, but any item of equipment however good can fail.

General good practice suggests that important equipment in the system should be backed up where possible. This is clearly not done in the case of lighting and display aquarium circulation pumps. Important as these are it is impractical and unnecessary to have a back up. In the case of circulation pumps, the aquarist could have a spare in the cupboard, but the loss of some circulation for a short period is not a problem so this is unnecessary.

One of the most important areas in an aquarium is the bio-filtration. Some would argue that it is the most important area as without it the whole system will fail, that is the livestock will suffer or be lost. So if canister filtration is the method in use, two canister filters are a good idea in case on fails.

Anyway, to get back on track. The return pump. Seawater gets to the sump by means of gravity and an overflow in the display aquarium. It flows through the sump and is pumped up again. Looking at the pump and its job, is it important enough to require a backup and if so is it practical?

One of the benefits of a sump is that it can house items such as a protein skimmer, heaters and possibly a deep sand bed (DSB). This being the case it would be detrimental for seawater not to be exposed to the protein skimmer for a long period of time. Similarly, the seawater needs to be maintained at the proper temperature. So the flow through the sump needs to be reliable. So a back-up is desirable.

One of the items that the aquarist should check when at the aquarium is flow, and a lack of flow from the display aquarium to the sump is very noticeable. Seawater loses heat slowly (the loss rate being subject to circumstances) so heat loss is not of great concern, the loss of flow should be noticed before any problem arises. The lack of flow will not be noticeable on the protein skimmer as it will continue to function though will fail to remove organics as they are not going through the bubble chamber. Any DSB will not be affected as seawater is present, though benefits such as nitrate reduction could temporarily be interrupted.

From a practical point of view, a back-up return pump is best considered in the sump design stage. Many sumps have a sectioned off area that is capable of housing one pump only. If two are to be used, the sectioned off area will need to be that much larger, unless the pumps can be fitted one above the other.

If two pumps are to be used, should they be of equal pumping capacity? The guideline for the flow rate through the sump is around three times the net gallonage of the whole system, that is display aquarium and sump, per hour. So two pumps together need to provide this, each pump having one half of the pumping capacity of a lone pump, that is, each pump needs to be able to deliver around one half of the required flow rate. Both pumps are very unlikely to fail at the same time, and the failure of one pump means that the flow rate through the sump will be half of that intended. This will be enough to maintain heat distribution, and will continue to present organics to the protein skimmer. The DSB will also continue to function.

If the aquarist does not check flow rates when feeding or admiring the display aquarium, or uses an automatic feeder and doesn’t check the aquarium particularly regularly, then having two return pumps is a good idea. If checks are regularly made and the aquarist is confident that a changed flow rate, or lack of one, will be fairly quickly noticed, then two return pumps are not really necessary. Consideration needs to be given however to how quickly a replacement pump can be obtained should this be required.

The individual cost of pumps where two are used will be a little lower because of the lower pumping capacity, so the extra cost over one pump is not great. It is a good idea overall to protect important system functions where practical, and the use of two return pumps is good and follows this principle.

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