I remember as a youngster making a coal garden.
This consisted of a small rectangular fish tank with a little water in the bottom.Then a few nuggets of coal carefully placed in the water.The lot was then topped up by very carefully pouring a tin of egg preserver over them slowly so it didn't cause a lot of movement. A waiting time of 4 or 5 hours was all that was needed, slowly at first then more quickly greenery then colour started to appear and after a couple of days the tank looked like an underwater reef. The trick was not to move or nudge the tank and disturb things.
The egg preserver could be bought at the chemist in those early post war years but I doubted there is a use for it now.In stepped Google and I found it is actually sodium silicate which is used in a whole host of things and is widely available,the trouble nowadays would be finding the coal unless you live near Jenny. I was even more surprised to find people are still making something like them,the ingredients are different but the result is the same.You can also make a crystal garden in a similar fashion.Google have of images of them and similar ventures.
We had a camera of course but only the old black and white so photos didn't look spectacular.
I don't know what train of thought brought this piece of my childhood memories suddenly surfacing after almost 60 years.Our minds are a truly wondrous things. Did you make anything as a child you forgot about until suddenly it resurfaced in your mind?