Hyenas of aquatic world - Clea helena

Clea Helena (assasin snail) - There should be enough snails in the tank to keep them busy otherwise they tend to scavenge for food. Eat all the food that is on their way. 

Oryazis Dancena 

Oryazis Dancena - She was wild caught blue eyed beauty and was in my 4 foot tank for almost 1 and a half years. 

She succumbed to a major injury and was counting her last few minutes. She was struggling to keep herself up and that is when these predators came into act.   

The first five or six predator's suffocated her to death and within few minutes there were lots of them feeding on her.

It took just 2 hours of time for them to finish of her completely. Although they seem brutal, without them she would've died in some crevice unnoticed and increased the nitrate level in the water which would be fatal for all the other inmates in the tank. 

They bring the balance in the aquarium by scavenging the dead/paralyzed ones.