Coming closer to the garden pond, I can easily spot difference between fish brought from the shop and born in our pond. Shop-fish are shy and easy to scare. Fish born in the pond treat us like family. They behave like home pets, swim closer when we apprear and eat from hand :) Those from shop do it as well, but they are not so fast. I read in the net that that only koi do that. In our case this is carrasius auratus, which is safer to have in garden full of cats. Carrasius is much faster and faster runs away danger. Have a look how we feed them...
There is always a dillema how often to feed and whether to feed fish.
In well established and balanced ponds fish will find enough food, so there is no need to feed them. Overfeeding is harming the pH and eco-balance of water.
This year I had real trouble - water in the pond was in tragic condition - you could see trough just 2-3 cm. I had a real fight in the summer. The results will never be visible immediately.
Saying that it is a lifetime project to understand the delicate life balance in your pond - might sound scary, but each pond owner has to be prepared for that.
For 2 years my pond was crystal clean, without exchanging the water in the spring. Actually exchanging the water is one of the worst things to do - the balance has get build from the beginning. In the third year somebody spelled my pond!
Plants didn't grow and water became muddy. Why? I made 1 very serious mistake: in the first year I let 2 grass carps
ctenopharyngodon idella to the pond! I have red that they are growing big - I was on 'giganteus beginner mode', so it made me happy at that time :) - what I didn't know, that they eat 3 times as much as they weight daily! They are like WATER COWS! they will eat every plant in your pond!
We even started to scatter grass clipings on the surface of the water for them! To protect the water plants. It didn't help... I saw them few times getting out of water by 5-7 com and reaching to grass straws bending over the water and pulling them until grass gave up! It was scary at the beginning, but I got used to it - human nature. I hoped we can go on somehow. Unfortunately because they eat most of the plants, it is dificult to reach the balance in the water, due to lack of oxygen in it. We decided to remove them from he pond in the spring and let them to biig ponds in the neighbourhood - fishermans will be happy. Cleaning the water was very time consuming project, cos I had to clean the filters 2 times a day. Every time filtering media were dirty so much:
cleaning cleaning and cleaning and no real results. can you call little improvement after month of such treatment a result?
I tried many diferent ways. The best reviewed by users special liquid against green water (algorem produced by tetrapond) made my pond looking like this:
Also harmed plants - they became brownish. I made everything according to the instruction and quality of water didn't change.
I do not want exchange the water - I want it get balanced!
So I decided there must be better, more healthy way. I heard something about acidic peat but I was not sure what peat is should be. First I thought reglar one will do, but nope! I learned it has to be special! I found it and I packed my regular filter with fibrous acidic peat (it has to be fibrous and fertilizer free) and zeolite.
Peat is adding to water some humus acids that fight algae in the water. Algae are allergic to it.
Zeolite makes water softer - it absorbs ammonia, stabilises pH and keeps the organic waste on proper level.
That was it!!
After 2 months water looks much better. Have a look by yourself:
These pictures were taken on November Sunday; water is clean and healthy. So just after winter, next season will be much better.
As somebody said: "There is nothing better than garden next year".
Filtering device is still outside, not hidden elegantly yet. Why? No enough time this autumn. There was more emergency cases. 
In the buckets on left side there are water plants, that I didn't want to place in the pond, so fish will not eat it. Now I don't know whether to keep them like this through the winter, or to put them to the pond?
These are great trees of neighbours, that made me fall in love with this site and buy the house and non-existing garden... soon years ago.
Very thin cover, rather sugar powder scattered around... 
