Months ago I bought some small Koi. They didn't do any good. Then I bought four 4" Koi for our fountain and they did great. They would eat out of my hand. Then I noticed they became very frightened, and two disappeared. I chalked it up to cats or Kookaburras. I bought two more, but now the four have become even more afraid to show themselves and hide on bottom, in the plants. I haven't fed them in a week. They refuse to come out, but appear healthy, just not active.

Does anyone have any experience with these rascals.

I've some experience with them through some landscaping ventures. I know that they do need some cover for protection from birds and such. As far as staying on the bottom and not feeding much, that just sounds like wintertime metabolism dormancy to me. Are they inside or outside? Keep in mind that they are really just colorful carp.

They are outside, but it is summer here. Water temperature has been around 27 centigrade. I thought maybe that was keeping them down. They act exactly like the dormancy I see in winter when the temperature drops below 10; stationary, like they are sleeping, but not.

The two that disappeared were the most colorful (easiest to see); one gold, one orange and white. The people here say if you find pieces of fish, it's a cat. If you find nothing, it's a bird. Must be a bird. I've started covering the fountain at night.

If the fountain is not running, it could be an oxygen problem, although the carp, like goldfish, are not supposed to require aerated water. If you ever see them near the surface acting like they are eating floating food, but there is no food, they are really trying to breath. I have no reference for how hot 27 C is, but fish feed best in a zone, too warm isn't much different than too cold. Of course you may be right about predators, if they are simply disappearing, that's the obvious answer. Good luck.

I just went back and saw that you said they are 4" fish. They would certainly be small enough to be easy pickings at that size. Is the water at least 2 ft. deep?

27C is about 81F. Water to 30C is supposedly O.K.

The pool is about 2' deep. The water is recirculated up and drops in a large bowl, then drops about 3' into the pool. Aeration is good. PH is good. I've got three large plant pots in the pool, and two water lilies that also provide cover. They have plenty of places to hide. They tend to just sit on bottom behind one of the pots in the back. I haven't fed them in a week, and have not seen them swimming around in about that same time frame. I'm assuming they are eating something. They certainly aren't acting like they are hungry, and no one has turned belly-up like they are starving.

From what you are saying, their behavior doesn't sound so out of character to me. I've never dealt with them in an environment as small as a fountain, but I wouldn't expect them to get very big in there. We generally use them in a pond setting with a "deep" end and a shallow end. The deeper part may be as little as a meter. Generally they are colorful enough to be seen all the time except when really hiding in thick vegetation, especially in larger ponds where they will get fairly large. I've never seen any tame enough to eat from a hand though.
Hope you find someone more knowledgeable than me.