Koi's - Header image

Fish pond maintenance tasks and schedule

Maintaining your fish pond has to be the key factor to keeping your fish successfully all year round, after all why spend all of that money building your fish pond just to let it go to ruin afterwards by not looking after it. Developing a routine for the tasks that are involved does not take long to realise and after a while the same tasks will become second nature to you. None of the tasks involved are too demanding and most of them are common sense anyway.

I like to look at the fish pond through the seasons of the year as different seasons do involve different tasks although some of these are also performed throughout the year, some on a weekly and some on a monthly basis. When the fish pond is first set up tasks like checking the water parameters will need to be done on a more regular basis as will the inevitable task of controlling algal outbreaks until the water parameters settle down and the fish pond matures. Your fish pond will be slightly unstable for the first few weeks after the cycle but keeping it well maintained will win 90% of the battle to make it a successful home to house your fish for years to come.

The most dangerous months for the fish are through the winter as the water temperatures drop and the fish go the the bottom layers of the fish pond, the water surface will attempt to freeze over, looking forward from the spring months to prepare the fish pond for winter should ensure no loss of livestock during these harsh times so this is the first season that I would like ot talk about and the other seasons will follow on.

Springtime is the time of the year that I always like to think about dusting away the cobwebs of winter and giving the fish pond a good clean up, just like we spring clean around the house. The water temperature is just starting to rise gradually so the earlier in spring that we start the better, letting the water temperature rise beforehand can mean leaving the water unbalanced, like many fish pond keepers I always closed down the filtration system during the winter and now is the time to get it back up and running before ammonia and nitrite levels rise sharply.

What better time to clean out the fish pond filter than now, the sponges or all media that the filter contains will have stood for a few months and will probably need a good rinse ready for action. If your filter has a UV built into it then check that the tube is working, the tubes also have a shelf life, normally of about 6 months. Check that the tube is in date and if not replace it before use making sure that the filter is switched off before removing the cover. IF you are running a separate UV unit then the same rules apply. Biological starter cultures will need adding to the fish pond to get the beneficial bacterial colonies growing again and once the filter is ready to go, power it up and get it running. Check that any pipework isn't blocked and that the water is flowing through without being hampered, more importantly check that there are no leaks, if so replace the faulty pipes immediately.

Now is the ideal opportunity to clean the bottom of the fish pond, debris has been laid there over the winter months and fish waste will have accumulated so if the pond is shallow cleaning is not such a major problem, for deeper ponds I recommend the use of a fish pond vacuum, these can suck out the debris and waste in a very short time making the task a lot easier. If you do not have a fish pond vacuum it may be necessary to drain the fish pond to clean it properly, make sure that all equipment is turned off prior to doing this and move the fish into a vat that contains water from your fish pond.

Any marginal plants that were overwintered out of the fish pond can be replaced and any plants that remained in the fish pond are probably showing signs of browning after a few frosts and snow during the winter months. All of the brown and dead leaves or stems can be removed as they will soon be replaced with new growth.

Check that the water level in the pond is at the required depth and top up with conditioned water if necessary.

The fish will become more active in the spring but don't be tempted to start feeding them to build them up, a couple of light feeds with a low protein diet will get their metabolism quickening without blocking their digestive system. Water temperature does dictate how well the fish can digest their food , early spring the water is only just starting to warm and the fish will still be a bit sluggish, build up the quantity that you feed them gradually.

Tidy up the borders to the fish pond and it may also be wise to check out any electrics that are wired to the fish pond equipment to make sure that everything is running safely and all connectors are still water tight.

It is not long before we drift into the summer months and the filters should now be up to speed and maintaining the water quality at a high level, the plants are growing and some may even be starting to take over the fish pond if the water temperature has aided them, the fish are now active and hungry so once summer is with us we can begin to feed up the fish, however all is not always rosy in the summer. The increased water temperatures can bring on lower oxygen levels in the water, the extra fish food added to the pond can be left over by the fish and algal blooms can occur due to the higher nutrient levels in the water. Testing the water quality on a monthly basis will pre warn you of any looming problems with the water quality so get into a routine of bringing out the testing kit once a month to see what is happening in your fish pond.

If the filtration system is adequate for the water volume and the bacterial colonies have grown large enough to cope with the extra bio-load that is being added to the fish pond, there should be no problems, if the nitrates are rising then perform partial water changes to keep them in check. If the oxygen levels are also depleting you will soon realise as the fish may rise to the surface gasping for air, adding a fish pond aerator should overcome this problem, if you have a waterfall or fountain running these should also replace lost oxygen in the water by the gaseous exchange that they perform.

Keeping the bottom of the fish pond clean will help the filtration system as more detritus is removed before it gets the chance to break down, so always keep on top of the cleaning maintenance at this time of year.

Unfortunately sunlight not only helps the pond plants to flourish but it can also encourage blanket weed to grow on the surface of the fish pond water, some fish pond keepers like to see some of this as, being a floating plant, it will consume some of the nitrates, but if left unchecked it can soon take over the whole water surface blocking light from the plants at lower depths. I made a simple tool for removing the problem weed, it was simply a stick with several nails along the length and dragging this through the water pulled most of it out, I did this on a weekly basis during the summer to keep it all under control but there are also treatments that you can add to remove the weed if you want it eradicating completely.

Algal blooms should be kept under control if there is a UV unit running alongside the filter, if not yet again there are treatments that you can add to the fish pond or you can even resort to the old trusted method of adding barley straw for a quick solution but his does not always work on a long term basis.

The key to success in the summer months is to keep testing the water, observe the fish at feeding times to make sure they are not showing any signs of problems and more importantly are accepting the food that you are offering them, keep checking the pond equipment to make sure that it is running efficiently and that there are no blockages in pipework etc.

Sadly summer seems to come and go very quickly and it is not long before we start to enter the autumn season, the days start to pull in and the air temperature may drop slightly. The flora around the garden will start to die off and shed their leaves especially the trees, this is generally the season where things start to slow down and now is the time to really start thinking about getting our fish pond ready for the long, cold winter months.

The plants will need to be tidied up and any marginal plants that are placed around the fish pond will need to be trimmed back before dead foliage falls into the fish pond. Make sure that any plants left in the fish pond can withstand the winter months, if the plants are not hardy they will die off with the first few frosts, keeping the plant labels when you purchased them will provide you with the required information.

Any plants that are not hardy need to be removed now before the frost has the chance to attack them, at this time of year the temperature can drop suddenly and you can find yourself being caught out, remove the plants before you are!

An excellent tip I was given many years ago by a fellow fish pond keeper was to place some fine netting over the fish pond in the autumn, this will trap any leaves that the trees are shedding before they land on the water surface, even if you do not have trees next to your fish pond, autumn is renowned for windy conditions and the leaves can easily blow over from the neighbours garden, this was quickly found out by myself and the netting saved me a lot of work.

Your fish will still have a voracious appetite but you do need to cut down on the feeding now, the fish need to slow down their metabolism so revert back to the low protein spring feed and reduce the number of times that you feed the fish, with the cooler water temperatures you will probably notice that the fish start to inhabit the lower levels of the fish pond, a good sign that they are slowing down.

The water quality needs to be as high as you can get it before the ponds goes into shut down during the winter, perform a larger water change and give the bottom of the fish pond one last clean during the autumn, the pond vacuum makes sense now! Test the water to make sure that you are on track and start to reduce the flow from the pond filters, in a few weeks they will be shut down anyway. Have a last check of the pipe work and clean out if required. Towards the end of the autumn period your fish pond should be ticking over ready for the long winter months of seemingly inactivity.

As autumn draws to an end the water temperature will drop dramatically and the shut down will have started but if you have performed the maintenance correctly, your fish and pond plants will be able to survive the winter months without any unforeseen effects.

Immediately prior to the onslaught of winter there are a couple of jobs that I do like to undertake. My filter is now closed off so I always remove the submersible water pump and check that all inlets and outlets are clear. This will not be replaced until the spring when the filter is kicked back into action.

The fish pond de-icer is taken out of storage and checked over ready for use when the temperatures are expected to plummet, allowing the fish pond to freeze over also allows toxic gases to become trapped underneath. These can become absorbed by the water and prove deadly to the fish, the pond de-icer will not keep the entire water surface from freezing but will keep one are open so that these gases can escape. In conjunction with the fish pond de-icer it is also wise to run a fish pond aerator, the aerator will keep the oxygen levels to the correct level and also speed up the process of eliminating the toxic gases into the atmosphere.

You may say “fish pond de-icers cost a lot of money”, if you are on a tight budget there is another method that you can use which is not as effective but still helps a lot. Float a hollow ball or a piece of polystyrene on the water surface, as the breeze moves these about it makes it very hard for the water to freeze, this method is often used in the smaller fish ponds that simply do not have the room for extra equipment.

If the worst does happen and the fish pond does freeze over, do not be tempted to smash the ice, this does more harm than good. Smashing the ice can produce shock waves through the fish pond which in turn can shock the fish, if you do need to thaw at all, pour some hot water on the ice and then use one of the methods above for preventing it from happening again.

It is natural for the fish to go to the lowest depths in the winter, if your fish pond is deep enough there will be no problem, if it is less than 3 foot deep I would seriously consider removing the fish and keeping them indoors until the warmer weather returns in the spring.

If your fish pond has been maintained throughout the year correctly then it will be fine over the winter, think of it as tucking the fish in bed for a few months, but obviously a lot colder!

Question left on Sat, February 4, 2012 6:13 am by Gerry

I've got a small pond with about 10 fish gold fish and shubunkins, the pond is frozen over now the last 2 days, should I have (put something) in there like a ball? Can I break the ice? *by pooring warm water over it* perhaps, I just hope they don't die.

From Gerry

Answer by staff: Hi there, floating a ball is an ideal solution to prevent ponds from freezing over and if you have a small pond then the depth of the water may not be enough for the fish to sink to. In this case I would defrost the pond and then add a floating ball to prevent any mortalities.
Question left on Sat, May 12, 2012 07:35 by Jose Sebastian


I noticed some circular transparent designs on the surface of my small pond which is actually a styrofoam container filled with water that had turned green. I was wondering if you can tell me what made those circles. I took pictures of them if you want to see them. Thanks.

Answer by staff: Pictures would help but I am guessing that either something has polluted the water to form oily rings on the surface, do you have any fish in there at the moment as some foods release proteins into the water and the same effect will occur. I would suggest that you perform a small water change and add a very small pump to keep the water moving to prevent this.
Question left on Tue, 12 Mar 2013 16:12:18 by cindy

Can I put fake lilies with a polystyrene bottom in my goldfish pond? I guess I'm asking if that would hurt the goldfish?

Answer by staff: You can certainly add false plants to a fish pond but I would be a bit concerned about using polystyrene bottoms to them as the fish may nibble at the bases and you would end up with polystyrene floating all over the place. If you do wish to use these I would add a weight to the base and then cover all of the base with a protective membrane such as sackcloth or even a plastic covering to prevent the fish from getting to them.