Q&A for How to Preserve a Starfish for a Decoration

Avoid using bleach as it will dull the coloring and break down the calcium carbonate that gives the sea star its structure. Placing the dried specimen in a freezer is a better alternative you can try after using the alcohol to further clean it without ruining it.

Yes, you can but be aware that it may not work. Make sure the starfish and sand dollars are clean before applying the clear spray.

It should be as simple as dissolving the salt. Try wetting a toothbrush with water and gently running it over where the built-up salt is.

In general, yes, if its alive. Killing any creature purely for decoration is unnecessary and potentially involves suffering for the animal. If it's already dead, no, it's not cruel.

You probably put it in freshwater, not saltwater.

You could put shellac on it or spray it with clear paint so it does not decay.