In the past year we had to change the water in our fish pond three times. The last time the pond water gone milky white, and we did not know what to do.
Our fish pond is small, we have a pump in place, with a mechanical filter and an UVC lamp installed. Nevertheless, the water becomes dark very quickly after we change it. But last time it became milky already the second day after I changed water, and on the surface I could see a thin layer that looked like an oil or something similar.
Naturally, my first thought was that perhaps I used tools that were not clean, but after checking everything it became obvious that I did not do anything wrong.
We were concerned about fish, but they behave normal. My wife was even suggesting that we change the water again, but we eventually agreed and decided to wait for a while to see what happens.
So the third day in the morning I was really worried of what I might see in the pond. Well, I could not believe my eyes when I realized that the water was crystal clear as it was on the day when it was replaced.
I tried to find some information about this, just like you are doing now by reading this text. But from the texts around it did not become clear what really was happening.
I have found some statements that this is due to some bacteria bloom which usually happens when such complete water change is performed. But I must say that we have not noticed anything similar when we previously changed the water, and we do the same steps every time. I have also found some statements that in most cases this problem resolves on its own.
As you realize, it turned out to be true. So the message is, no need to panic give it some time. Frankly speaking, we did panic though we did not know what to do. But you know now, so no worry if this happens at your side. Let me know how it was, there is a comment box below.