Our temperate climate is punctuated by four contrasting seasons, and our ponds change character as they enter each phase of the seasonal cycle. Even though we can be certain that each season will arrive, we can never predict the exact day, especially when taking into consideration other factors such as global-warming or localised climates.
Nevertheless, we know that spring follows winter, and that our koi are passengers on this relentless, yet logical seasonal cycle – we just don’t know exactly when it will happen. It is difficult and, if not impossible to draw a line in the sand between winter and spring, on what in effect is a continuum between the two seasons.
There are specific thresholds of temperature and daylength that will cause the pond and its koi to respond in a spring like manner – irrespective of the calendar date. And this winter – spring transition sees a temperate pond and its ecosystem slip from a state of slumber, rest and inactivity into a phase of preparedness, and gentle activity, ready for the summer – the season to breed and grow. So spring is the vital link between winter rest and vulnerability and summer growth and vitality.
The cold winter pond has enjoyed crystal clear water conditions, naturally high DO levels and relatively constant water chemistry. There has been negligible ammonia production, (any of which will have easily been processed by the pond’s micro-organisms), and depending on the amount of rainfall that may have diluted the pond water, things within the pond may have become a little ‘tired’.
The koi will have been inactive, resting in the deeper regions of the pond, and micro-organisms (both beneficial and pathogenic) will have declined. As the air temperature starts to rise to double figures, our pond’s temperature will lag behind, with the rise in water temperature also causing our koi to rise from their slumber.
The opportunistic strategies employed by pond micro-organisms will mean that they too will become more active, multiplying asexually to rapidly colonise this environment that is becoming ever more hospitable. As koi metabolism accelerates, no longer are they able to sustain themselves on their stored reserves of energy, but require food to meet their increasing energy demands.
Irrespective of the date, spring arrives when the water temperature hovers constantly around 8-10 degrees C. This is when koi demand regular food – something that starts an unrelenting chain of events for the whole pond. Just as a roller-coaster reaches the top of the first drop, from now on and to the end of the ride (or the summer) there will be no stopping the pond’s innate desire for life and growth. But we must ensure that we have covered all angles in this transition period, ensuring that when spring turns into summer, our koi are ready to fulfil their growth and spawning potential. There will be a number of factors to keep on top of during this period, and by doing so, we will keep the track clear so your koi can continue their growth momentum well into the summer.
Spring job checklist
1. Water quality
a. if you have left your pond alone over the winter, you will need to establish how the various interactions between your pond and the elements have affected your pond’s water quality. Nitrogenous compounds should not prove to be a problem, but nevertheless, for peace of mind, carry out a full range water quality health check. Action: Test pond water for ammonia, nitrite, nitrate, pH, KH, GH and salinity (if you salt your pond).
b. If certain tests showed a parameter to be unsatisfactory, then respond accordingly. Carry out a partial water change to reduce an accumulation of nitrate. If your KH or GH are low, or your pH has drifted down then use a source of calcium carbonate to buffer the water. Action: Respond as required to your water quality test results.
c. Pond water can also become ‘tired’ in an enclosed system. All living organisms will strip minerals out of your pond water, and excessive dilution of minerals by rainwater can also lead to the pond water becoming mineral deficient. The addition of a clay to water will help to restore the beneficial mineral loading that your koi will thrive on. Action: Add a clay to revitalise tired pond water.
d. As all organisms throughout your pond system start to metabolise at a faster rate, their demand for oxygen will also increase. Add to this the negative effect that a rising water temperature can have on water’s ability to hold oxygen and you soon establish the need to add extra aeration. The warming pond conditions now also make it safe for aeration to mix pond water. Action: Provide extra aeration in the pond and bio-chambers as required.
e. Water temperature will be the main factor to determine the speed at which both your pond and your koi will function. It will determine their appetite which in turn will affect water quality parameters, adding a burden on to your filtration. An accurate thermometer is essential for providing you with a reliable and instant record of your pond’s temperature. Action: Keep a log of your pond’s temperature with an accurate thermometer.
a. If you have used a pond cover over winter to protect your pond from the extremities of the winter weather, now is the time to remove it and dismantle it until the end of the coming autumn. Action: Dismantle pond cover and inspect for any damage that will need to be repaired before next winter.
b. If your pond is not fitted with a bottom drain, and your pump has been turned off over winter, you are likely to have accumulated leaf matter and other debris at the bottom of your pond. This should be removed before your koi become too active, by using a vacuum. Action: Hire or buy a pond vacuum to remove settled debris from the bottom of your pond.
c. It is wise to isolate waterfalls during the winter months to keep their chilling effect from cooling the pond water. Inevitably, pools within the cascade will also have collected debris which will need clearing before turning the waterfall back on. Also ensure that debris has not settled inside standing pipework as this could cloud your pond water. Action: Clean out waterfall and pipework before reconnecting to your pond.
a. Check that your filter is rejuvenated with all the care and attention required a achieve effective biological action (see article: kick-start filters). Wash correctly and check the condition of your filter media. Renew it now if required, instead of in the middle of the season. Action: Kick-start and rejuvenate the bio-activity of your filter.
b. It’s unlikely that you will have been using a pump and UV if your filter required to kick-start. Check that the seals and impeller of your pump are cleaned and that any pre-filters are renewed if required. Likewise, the quartz sleeve in the UV should be checked for lime scale and other dried material that could reduce its performance in the coming year. Action: Check the condition of pump, pre-filter and UV quartz sleeve and bulb.
c. If external fixed pipework has been out of service over winter, check that valves, taps and manifolds are in good working order. Seals can perish and pipework become brittle at low temperatures. Action: Confirm the integrity and function of pipework, including valves and taps is satisfactory.
a. Koi should be offered food when they start showing an appetite, which will be around 8-10 degrees C. This will immediately start to burden the bio-filter with an increased ammonia loading – so beware. Action: As soon as you start feeding your koi for the first time this spring, keep a check on the nitrogenous compounds in your pond, especially ammonia and nitrite.
b. Koi do not have a high potential for growth at these low spring temperatures, so a diet containing 20% protein should be sufficient. If a higher protein food is offered at these temperatures, then it will lead to excessive ammonia production in your pond. Action: Offer a low protein diet (20%) which will prove better for your fish and better for your filter.
c. Don’t expect your koi to eat in large quantities. They will be browsing for food in a casual manner for the next few weeks (rather than the feeding frenzy we experience in the summer). Action: Food should be offered on a basis of a little and often.
5. Koi health.
a. If possible, and while your koi are still quite sluggish, net each of your koi and bowl them for a closer inspection. Koi that have been inactive over winter may have developed sores or ulcers on their ventral surface; Something that will only become evident when inspecting them in a bowl. A close inspection also allows you to check and address any localised fin or scale damage. Action: Bowl and inspect koi from head to tail while your pond water is still cool.
b. When your koi are surfacing to feed for the first time, check the behaviour and deportment of each of your koi. All of your koi should show normal behaviour, with none swimming on their own and none holding themselves in an abnormal position i.e. head down etc. Action: Observe koi behaviour, looking for signs of ill-health.
c. After the first weeks of feeding, when the water temperature is above 10 degrees C, it would be wise to carry out a few mucus scrapes on your fish to check for the level of parasitic loading. Most fish will show a naturally low number. Watch out for an explosion in parasite numbers as the water temperature rises, especially if you experience a nitrite problem through a filter that is struggling to keep up with the rate of ammonia production. Action: Regular mucus scrapes in the early weeks of spring will identify any parasite problems before they proliferate.
Spring can be a risky period for koi as they fire-up their metabolism for the first time in months. You should wean them onto an appropriate diet while keeping a check on their behaviour and the performance of your bio-filter. By following the checklist, you should ensure that your koi, and your pond as a whole will slip from their winter state into spring, which is their warm-up for their vital summer growth and breeding phase. Get your koi ready in spring, by providing a stable and supportive pond environment, then they will reach their full potential in the summer. But be on your guard, as spring may be upon us any time between February and April, and when it does arrive, you must step in to prepare your pond and koi for the coming months.