The Pond Year
by Terry White
Spring
Photo by Everything is Permuted 
Spring is a bad time for pond fish. Temperatures are right for parasites and bacteria to multiply but the fishes immune system has not yet kicked in and they are at a low ebb after the winter.
A word of warning though before you reach for you pond treatments; first check your ammonia and nitrite levels as these will make the fish flash (scratch themselves on the pond sides/bases and gulp for oxygen)
There is no point chucking malachite / formalin, acriflaverin et all into your pond and stressing the fish more if it is just a water quality issue.
The rest of the pond is waking up after the winter lull, frogs are beginning to feel the tug of the season and will be visiting the pond at night to spawn. Frogs can sometimes get carried away and attach themselves to the fish with a vice like grip which, if around the gill plates, can suffocate and kill the fish. They may also hold each other under water too long and drown.
Photo by Everything is Permuted
Goldfish will also be starting to feel frisky and males will develop a spawning rash (white pimple-like spots on the gill plates and pectoral fins) and can be seen chasing the females around the pond.
Newts will be returning to the pond after over wintering in compost heaps and other places and the first of the insects will be hatching followed by birds and other wildlife.
Plants are starting to shoot and no longer look like dead pots of gravel, so clean up any of last year's vegetation that is left to let the light in for them.
Filters will be in need of a clean before the biological activity starts in earnest but beware of feeding more that the filter can cope with. Ammonia levels can rise fast so do some water tests on a regular basis until you are sure it is working fine.
Predators such as herons will be nesting soon and are always on the lookout for a free meal. Watch for them in the early morning and make life difficult for them so they find their food elsewhere.
Algae, both green water and blanket weed, will be starting to grow so now is a good time to change UV bulbs and check quartz sleeves on the UV clarifier. Take measures to curb the blanket weed, of which there are many different species and cures. The trick is to find one that works on your pond and use it before it gets out of hand.
All that said spring is also a time of growth, life and fasination so take time to watch your pond wake up and enjoy the start of a new pond year.
Summer
Photo © Pond Life
Now the temperatures are starting to rise be aware of a couple of potential problems that can come your way.
Biological filters will be stretched to the limit, the temperature affects a lot of factors; use your test kits to find out every so often or if you think their may be some problem, it's the only way to find out what is going on. Ammonia, Nitrite, Oxygen and pH are the main ones to watch.
New filters may not have established yet, old ones are not checked and cleaned as often as needed, the fish are a bit bigger than last year, maybe you have added some more or they have multiplied.
Dissolved oxygen levels fall as the temperature rises and the fish, which were fine at 15°C, are now hanging near any water outflow gulping at or near the surface or found dead in the mornings. Be especially observant on muggy nights or during a thunder storm as they can be very detrimental to a pond's oxygen levels; so too can that rampant growth of some water plants. All plants reverse photosynthesise at night (emergent plants take most of the oxygen from the air) but where do you think the submerged plants get it from?
If the available oxygen is low the filter bacteria are also finding it hard to breathe and so limit filter growth and the potential to break down all that food the hungry fish are consuming (if your fish are not eating at this temperature you have a problem.) All that food is being processed and excreted at a much higher rate than it was in the winter.
If you are into koi be sensible about KHV. If you are buying koi quarantine them in reasonable surroundings for between 4 - 7 weeks (most outbreaks should have shown by now but not all) at temperatures above 22°C and report any reasonably suspected sources. If you haven't got the quarantine capacity perhaps you should sort that out before buying new fish.
Above all spend some time with your pond (a glass or two of wine helps but is not mandatory) it's not just watching the fish but the birds, animals, insects, plants, sounds and reflections that makes a summer's evening by the pond relaxing.
Autumn
Photo by Kathleen Tyler Conklin 
Autumn is a time to ready your pond for winter. The nights are drawing in and temperatures dropping along with the dreaded leaves. Cut back water plants as they brown and die back and net out falling leaves, this will save it rotting down in the pond over winter. As deep water plants like lilies die back and open up the pond surface I like to have some water hawthorn (Aponogeton distachyus) because they are just starting to come up, are at there best in spring and autumn and will give you some winter colour and cover.
Floating plants like water lettuce and water hyacinth will die off with the first frosts and should be removed now as the don't come back in the spring. Either store some in a bucket in a conservatory away from the frost or buy a couple of them next spring and let them reproduce again when the frosts have stopped.
Filters should be cleaned and tiptop condition before the winter as bacterial activity will be slowing and the less work they have to do the better.
Most fish will be slowing down as the water temperature drops (not sturgeon; they will want food all year round) but the fish should be at their heaviest weights to get them over the winter. I tend to feed the fish in the mornings once the water temperature drops to 10°C, especially on good sunny days but smaller amounts.
Autumn is also a time that the parasites start to multiply rapidly as the fishes immune system is slowing down. Don't automatically treat them, just be observant for any possible problems starting.
Water quality should still be very good, do some water tests to confirm this. Oxygen levels should be rising as the water chills down. Some poeple turn off air pumps over the autumn/winter period because they pump cold air into the pond water. I leave them on as the heat generated by the pump tends to negate this and I like to have a lot of air in the system.
Remember there is still plenty of time to enjoy your pond over the autumn but it's best to get the work done before the water gets too cold. Spending a long time with your hands in cold water in January and February is no fun.
Winter
Winter is a quiet time for pond keepers, the fish and filters are at a low ebb and there is hopefully not much to do. You should as a matter of course check the temperature of the pond and do water tests.
You can feed the fish, especially if you are a day or two into a settled warmer spell, but only a small amount at a time. Sturgeon will need feeding more regularly as they can lose a lot of weight over winter if not fed for days on end.
Keep pumps running, as this should stop the water freezing up. If you do turn them off make sure no water is sitting in the ultra violet light casing, as it will break the quartz tube when it does freeze and they are expensive to replace. If the pond does freeze don't break the ice, it will scare the fish. Melt a hole with a warm pan of water and take out an inch or two of pond water creating an air gap under the ice, this will allow oxygen and other gases exchange.
Filters will still need to be checked on a regular basis and cleaned if necessary.
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If you do heat the pond keep it below 10oC or above 16oC, the bit in between is a haven for parasite and bacterial problems and the fish are very susceptible between these temperatures as their immune system only works above 16oC.
Koi will be sulky, tending to stay in the deeper water and often will just sit in the same spot for hours almost dormant but should still feed and be active on nicer days.
Look out for visiting birds around the pond. Each year a grey wagtail takes up residence at our pond. It (Bob) arrives near the end of November and stays until the ducks start nesting in mid February, feeding on the last of the insects and the occasional fish food pellet. Magpies have also worked out they can grab the odd pellet from around the sides of the pond but, on a more worrying note, a little egret has also been taking an interest in our smaller goldfish pond and we have had to place tripwires around it to discourage it.
Above all stay warm, the water is bitter cold. Maybe plan what you want to do with the pond over the spring and summer in front of the fire with a warming drink.
