My starfish has died :(

I have some bad news guys... Seems it is indeed very hard to keep marine invertebrates in aquarium. My starfish has died last week. I did not notice anything at all and it happened almost overnight. What really struck me was that the starfish was perfectly well the day before, and on the day it died, it simply started to 'melt'... Yeah, it seemed to me that it was melting and disappearing in the process, leg by leg... I counted the leg from 5 to 4, 4 to 3, 3 to 2, 2 to 1 and finally nothing... And all this time, it was still alive and moving about... I was totally battled by this scene guys... However, I do not have any more information on what happened or why it happened. I have some of these big snails which has a small trunk... I watched some docs on television and I remember they are predators and have a toxic sting which they use against their prey... I have not idea what happened, it could be that the starfish was stung by one. However, I am really sad and sorry about this.

The good news is, I have introduced some live aquatic plants in the tank and they seem to have settled down in the bed and have started growing... I hope they will render the water safer for the animals by sucking the nitrates and other nutrients from it and prevent them from contamination the water. Let us see how it goes.... Maybe, after that, I will go and look for another starfish as it was really the eyecatching point of my aquarium.