Sea cucumber got shreaded in powerhead

[s.holmes]

Hey guys, i am new to all of this. I have a 25 gallon reef tank.2 days ago i went to my LFS. And not knowing much about sea cucmbers i bought a orange one because it was super cool.... But what wasnt super cool was how the next night it got sucked up in my powerhead and poisioned my tank. When i woke up all my fish had died and my corals were not happy. I did a 70% water change yesterday and im running carbon right now. Everything is looking good again today. but just wondering if anyone else has had a experence like this and how long did u wait to add fish again? thanks for your replies in adance .