Your pond looks very nice and you are making some nice improvements as you go.
First before you get any new fish I would think you need to figure out if you can what happened to your fish. When was the last time you saw them? Do you have heron or similar birds that might visit or raccoons, snakes etc? Any idea's? You might need a net to keep the new ones safe.
Hens and chicks are what most call those little plants but the scientific name is Sempervivum tectorum
Found this interesting bit of info on the net:
Sun and Soil Requirements for Hens and Chicks:
Grow hens and chicks plants in full sun to partial shade and in well-drained soil. In the South, hens and chicks can profit from partial shade; but the requirement for well-drained soil is a must in any zone!
Care for Hens and Chicks:
The "hens" will die after flowering, but by that time they will have produced numerous "chicks" or "chickens" to take their place. To propagate, simply split off the chickens from the parent plant and transplant them. Providing contact with the soil should be sufficient for transplanting, since hens and chicks root readily.
Origin of the Latin Name for Hens and Chicks:
While the origin of the common names, "hens and chicks" or "hens and chickens" is apparent from the foregoing, the reader may be curious about the origin of the plant's Latin name, Sempervivum tectorum.
The word for the genus, Sempervivum, is Latin for "always live," i.e., evergreen. So far, so good. But when you discover that the word for the species, tectorum, means "on roofs" in Latin, you may start scratching your head. What does this evergreen perennial have to do with roofs?
Well, it turns out that hens and chicks, which are indigenous to Europe, were traditionally planted in thatched roofs. European folklore held that they were supposed to provide protection against lightning-induced fires, due to the plants' association with two gods of lightning: Thor and Zeus (Jupiter). In this case, folklore is justified, in the sense that succulents such as hens and chicks are fire-resistant and would perhaps slow down the spread of fire through thatch.