The first question is ‘to feed or not to feed’?
As a rule of thumb it is safe not to feed if your pond’s stocking density is low (less than 100 grams per cubic meter (1000litres) as the natural food in the water will sustain your fish. Often the stocking densities are much higher than this in garden ponds because over the warmer months the fish have grown big with lots of lovely filtered, aerated water and delicious food. Similarly recreational fisheries can have stocking densities much greater than this.
The fishes’ feeding requirements in the Winter are potentially difficult to judge because they often appear keen to eat swimming toward the edge of the pond as you approach with mouths agape. This is just learnt behaviour (a Pavlovian response), a hangover from their competition for food in the warmer months. Although they look keen they actually will only eat a morsal or two. What they eat they will digest poorly as the water temperature makes their ability to digest inefficient. Their actual requirements are only for maintenance not for growth. Again as a rule of thumb you should not be feeding more than 0.1% body weight. So a one kilo fish only needs 1 gram of food (2 pellets!)
The second question is ‘what to feed’?
Because the fish is unable to digest the food efficiently at low temperatures it is important to feed a diet that has low fat levels. At Hampshire Carp Hatcheries we change our Summer growing diets of 42% protein and 18% lipids(oil) to low energy Winter diets of just 33% protein and 6% lipid. The characteristic of this food is that it is light in colour like Weetabix! This means that the fish are able to utilise almost all of the ingredients and are not excreting out waste with a lot of undigested food in it. Any undigested food will cause your ammonia levels to rise causing your fish to suffer.
The final question to ask is ‘how can I be sure that I am not over feeding’?
Overfeeding in the winter is a dangerous practice as the waste food quickly becomes toxic and the water quality deteriorates. Over the cold winter months the fishes’ immune system is weak and they are vulnerable to infections and pathogens.
On our farm we have a simple and cheap solution to this question. By the edge of each pond, we peg down a washing-up bowl on the end of two poles so that it sits on the pond bottom.
When the pond is fed, a small amount of extra food is scooped into the water just over the washing-up bowl. The following time we wish to feed we first check the bowl to see if all of the food has been eaten.
If there is no waste food in the bottom of our washing-up bowl we know that we are not over feeding.
If there is some left in the bottom we know we have a problem and we MUST NOT feed anymore.
As fishfarmers, fishery managers or pond keepers we will want to understand why they haven’t eaten their rations. There a 3 possibilities
1. We’ve just fed too much!
2. Poor water quality
3. The fish are sick
If it is overfeeding then hold off feeding again for at least 10days, to give your pond time to recover and then try a few pellets chucked in over your feed station just to see.
If the ration hasn’t been eaten because of waterquality or fish health issues then we will need to investigate further but that’s another blog!