Siobhan,
The Glitter Germ can be an excellent prompt for the children to start an investigation inquiry.
After they have seen the demonstration they should try to construct an explanation of what they have seen. Then they will have questions that they can investigate to confirm their understanding.
You might consider offering a range of liquids that could be added to the glitter water – The Children’s Museum of New Hampshire has a nice description of some possibles (toothpaste, cooking oil, hand soap) and outlines the science behind why different liquids behave differently.