Definitely water Hyacinth in the upper pic. Some sort of iris or rush-like thing (grassy looking vertical leaves) I would try to use variegated Iris. Neatest, least invasive.
Background is some fern. Australian Tree Fern has fronds like that, but so do many other ferns. To the right/middle looks like Agapanthus, thick strap shaped leaves.
2nd pic: Hanging over the edge is Myriophyllum. Try to find a dwarf. The most common is a rampant weed in a setting like this; even the dwarf will need trimming to stay small enough.
Some sort of water lily floating leaves. There are some dwarf varieties to look for in a planter this small.
Fine spiky thing might be any of the smaller rush/sedge/papyrus sort of grassy thing, or a very fine leafed Iris.
In post 12 I think I see Bacopa (far right) in a pot with a low growing moss. You can grow plants in pots by turning one pot upside down in the barrel and sitting the planted pot on top of it. You could even cut a hole in the bottom pot to make a cave for the fish.
Background in pic in post 12 is Hosta (green and white leaves). I am not sure of the plant to the left, but Stachys would work like that, low growing, large leaf.