Koi pond pump filter failure

My Koi pond has been up and running for three years now with no problems. But when I went out to the pond this morning the water had stopped circulating down the waterfall and everything had gone quiet.

Luckily my neighbour who is also a Koi keeper came to my rescue with a spare pump.

Is there anything I can do to prevent my pump failing in the future?

What about my other pond equipment? And what if there is a power cut?

How do I ensure that my water quality and the health of my Koi is not compromised?

Koi are farmed under semi-intensive conditions which means that their stocking density is only slightly above what would be found naturally. Consequently, they will be offered a supplementary food, and may require additional aeration in the warmer months. The farm pond’s environment however will remain healthy and balanced without the need for pumps or filtration.

As koi keepers, we up the ante a little more by keeping koi at higher stocking densities than those they are farmed in, meaning we need to offer them more support in the form of a pumped filtration system.

In a koi farm pond scenario, as there is no pump sustaining the pond, there is no risk of a pump failure. However, if a pump fails in a koi pond, the consequences can be catastrophic as the pump equates to the heart of the pond, and without the heart, the pond will start to suffer.

I remember back to when I farmed koi for a living, the high-risk, heart-in-the-mouth period was when the eggs and fry were in the intensive recirculation hatchery systems for the first 2-3 weeks of their life. In effect, the whole year’s production was at the mercy of the national grid and the pumps’ reliability. It was a great relief to be able to move the fry out to the mud farm ponds and hand them over to mother nature where no power cuts or pump failures could harm them.

One of the more advanced hatchery systems I worked with had a back-up generator primed to kick-in should the mains supply fail. This was essential when considering the impact that a power cut could have on my livelihood, but is hardly practical (or economical) for a koi pond. Another safety feature was simply the daily observation of the noise levels within the hatchery unit. Consisting of prefabricated tanks standing on a concrete floor, you would soon become familiar with how the hatchery should sound. On more than one occasion, my attention was drawn to a change in the sound, caused by a high-pitched whine coming from one of the systems. On closer inspection of each of the independently filtered systems, I discovered a pump had developed a noise, indicating to me that it’s bearings were wearing and that it would need replacing before it failed completely.

As an aside, through trial and error, we found that running the systems on high-end garden pond pumps (rather than typical aquaculture recirculation pumps) was far more cost effective and reliable – a reflection on how demanding and competitive the garden and koi pond market has become.

With regard to your query about preventing another pump from failing in your own garden pond, you are asking a very difficult question. All pumps will have a finite life and may even fail or wear out within their guarantee, meaning that you should be constantly vigilant irrespective of the length of the pump’s guarantee. In a controlled environment such as a fish farm hatchery, it can be possible to spot changes in the ‘pitch’ made by a pump. This will be difficult in a koi pond situation where the pond is buried in the ground, insulating any noise a submersible pump might make. It is however much easier to detect wearing noises on an external surface-mounted pump.

All I can suggest is to undertake regular servicing and inspection of your pump, to check that the impeller and other moving parts are not impeded or choked by everyday pond debris such as blanketweed. However, most pumps prefer to run continuously rather than being stopped frequently for checks, so be sure to keep a balanced approach with servicing.

A pump’s life may also be shortened by subjecting it to additional loads and pressures, causing it to wear out prematurely. For example, if the pump has a foam pre-filter, be sure to clean this regularly so that a free-flow of water is permitted into the pump chamber. If the intake of water into the pump is restricted by a blocked foam pre-filter, then being water-cooled, it could soon overheat.

Likewise, on the discharge side, the correct choice of the diameter of pipe is essential so as not to create significant back-pressures at the pump – again potentially leading to shortening the life of a pump.

What about other pond equipment?

All other pond equipment is far less critical for the life of your pond and koi if they were to fail

UVc: The worst that could happen if this were to fail (electrically) is that you would start to notice your pond turn green. This is purely an aesthetic cost, and in fact could benefit your fishes’ colour and overall health – after all, that’s why the mud ponds of Niigata are green! Regular checking of the UV (particularly easy at night) to confirm that the bulb is illuminated is all you really need to do. Also, change the bulb early spring to ensure that it gives it’s best output when it’s needed most – in the summer months.

Air pump: The moving water through your pond and filter will actively aerate your pond and as soon as your pump fails, the DO levels in your pond and filter will drop immediately. Likewise, if you are aerating your pond and filter system with an air pump, hardware failure will lead to a drop in DO. This may lead to a dangerous decline in Do in the height of summer when the pond ecosystem, koi and biofiltration are all demanding oxygen at their highest rate. However, unlike the loss of a pond pump (which in turn will lead to the loss of filter function), losing an air pump will not lead to potential catastrophic conditions while the pond pump and filter are still in operation. You may witness an increase in lethargy, even gasping, in your fish, and perhaps a drop in some filter-related water parameters (such as ammonia and nitrite), but nothing that will threaten the life and maturity within you pond and filter.

Power cut?

If the power fails and the pump stops, then the speed at which problems start to develop will be dependent on the water temperature.

If the power failure occurs at winter then it is less of a problem as the dependency on circulation for D.O. and filtration are much reduced. However, if you are heating your pond, either electrically or by gas, then your koi are likely to experience a drop in temperature. Although not life-threatening, such unstable or extreme changes in water temperature are likely to stress koi, especially once power is resumed, when the water temperature rises to its original level.

Check that the power failure is not caused by an oversensitive safety device in your home’s consumer unit (fuse box). Individual circuits may have an earth leakage or ‘trip’ switch which will isolate the power supply at the merest hint of a faulty circuit.

Electrical circuits that leave the house for the garden, shed, or pond are more likely to experience conditions that will cause a circuit to ‘trip’. Exposure to the elements, rodents wishing to wear down their teeth or more typical problems with electrical equipment can all lead to the most sensitive of circuits to be isolated.

In such an instance, where the safety device does not allow the circuit to be reset, a process of elimination must be followed to isolate the part of the circuit that is faulty. It may be the underwater lighting, the pump, UV or electric heater (a likely candidate, especially in the winter). Once isolated, the system should be reset, and be able to run uninterrupted thereafter.

If the power cut is to the whole house, your efforts should be turned to maintaining a suitable DO for your koi, and to keep your filter media wet (if it is not a gravity-fed system). In winter, when DO levels are naturally high, this should not prove to be a problem, but in summer, will require some action depending on the length of the power cut.

During the power cut. If fish are gasping, cold tapwater can be sprayed from a hose onto the surface of the pond. This will also help dilute a build-up of toxins and increase DO. If your filter is the pump-fed trickle-type then periodically keep the media moist by pouring pond water over the media. Of course, do not feed during a power cut.

After the power cut. Carry out water tests for the next few days to check if the filter’s performance has been affected. The worse the filter has been affected, the higher the ammonia and nitrite readings will be. Respond accordingly with partial water changes as required.

How to maintain good water quality

You should be able to maintain good water quality if you lose any of your powered pond hardware, except the pond pump.

If your pump fails:

Ensure your pond and filter are aerated well with an air pump

Isolate the pump and seek a quick replacement

Stop feeding

If your filter is pump-fed, keep the media wet by periodically dowsing it with buckets of pond water

Upon restarting the pump and filter, test water for any negative impact the pump failure may have had on the filter.

What’s gone wrong? Your equipment has failed – but what’s exactly gone wrong?

All equipment not working:

1. Is your whole house experiencing a power cut?

2. If not, check the power supply out to your pond. Check your consumer unit.

3. If the supply out to the garden has ‘tripped’, unplug all pond hardware and reconnect sequentially to isolate the offending piece of pond hardware that causes the whole circuit to ‘trip’.

Single piece of pond equipment has failed:

1. If it has it’s own fuse, check the fuse

2. If still not working, remove it completely and double check by plugging it into a reliable power source back at the house

3. If still ‘dead’, find a replacement urgently.

Kill blanketweed and string algae.