It is very difficult to determine the meaning of a dream from a single snippet of information. Dreams communicate through symbols which relate to each other in the environment where the dream takes place. One fragment of one symbol, isolated from its context, has very little significance in any way. For example "a pond or water" could be in an urban park or the Amazon jungle or the Sahara Desert. In each case, the meaning would be very different. An interpreter could create a scenario built on that fragment, but the result would be a product of the interpreter's imagination, not a true analysis of the dreamer's experience.
This dream seems to be a message of comfort and reassurance. In your subconscious mind, there seems to be an awareness that your grandmother is not entirely absent but continues to bless you with her spiritual care.
The root word "pond" refers to a small body of still water, typically shallow and natural.
Solution of Pond Water= Oxygen + Water
The pond.
Pond water is not a pure substance.
Nothing, as the minerals that are found in soil would not be present in pond water; plus there would be no anchorage of any kind, which would mean if it did grow, it would blow away anyway.
Water bugs walk on water. So this dream might reflect longing to do the impossible or to rise above common problems.
The pond itself.
The pond itself.
Physical, but the pond does not chemically change - you still have water and pond goo, only the water has evaporated.
Some can be found in pond water but not all.
Better than what? I don't know exactly what you mean or why you ask, but bettas (assuming that's what you mean by fighting fish) need clean, chlorine-free water that is above 76° and filtered and at least 5 gallons to swim around in. You can't keep them in an outdoor pond and water taken from a pond is likely to have diseases that will kill them.