Clean the fish
First of all you need to clean the fish properly. You need to wash the starfish in warm water. Also, use small quantity of mild soap. Remember to be gentle while handling and washing the starfish as when they become dry they can be quite brittle and you do not want to break it. Use a fine brush to gently scrub the starfish and get it nice and clean.
Soak in alcohol
Next you need to soak the starfish in rubbing alcohol. Leave it there for two days. You can leave the starfish in the rubbing alcohol without even cleaning it.
Instead of rubbing alcohol, you can put a solution of formaldehyde and water. Mix one part of formaldehyde into five parts of water and place the starfish in it. This solution removes starfish odour and adds a chemical odour which lessens when the starfish is left to dry. Be sure to do this in a well ventilated area as the smell from the alcohol or formaldehyde can be quite strong and cause irritation to your eyes and nose.
Dry under sunlight
You need to completely dry this marine creature in order to preserve in a dry place at your house. You can dry the starfish by placing it on a flat surface under the sunlight. Remember that during this process, starfish’s arms should lie down and not curl up. In order to do this, you can place small stones above its arms so they lie at their places. Try not to put too much weight on the starfish legs as they can break or get damaged. Also, do not leave the starfish outside too long as you do not want it to get heated up from the sunlight hitting it.
Only preserve dead starfish:
If you find a living starfish on the beach then put it back in the water. You should preserve starfish which is dead. You can check that a starfish is dead if it feels limp. In case the starfish feels firm then it is alive. In addition to this, the feet of starfish which are located on the bottom side of a starfish responds if you touch the starfish. In order to whiten a starfish after completing the preservation process, you can simply put it in a solution of bleach and water. Leave it there for few minutes.