nope

recently I bought a computer magazine where experts claimed you should not use task killers on Android. I have a task killer installed on my Note 4 but I only use it if I get an app that crashes or wont allow me to quit. (although I rarely have that problem) it just saves resetting the phone in some cases. usually you can change what apps the task killer controls anyway in the app settings. arguably task killers dont work that well anyway, cos the apps it terminates just restart themselves after a predetermined time.

in android free ram is wasted ram.

What banbury and 3mel said. . I think many of us who came from Symbian and Windows Mobile have always had this thing in the back of our minds that if its in RAM its using battery and depleting resources, but these newer mobile OSs flip that mindset on its head. They cache the apps in RAM so that less resources are used when launching that app. The important thing here is that your Android phone or tablet must have enough RAM to keep the basics/priority apps running smoothly e.g. Phone, Messaging, PIM apps etc... and then whatever is left thereafter goes to 3rd party apps.

try Greenify (Root Mode) and you will see if Task killers are important or not** dont use these: 360 sercurity; clean master; apus; zero ... just try Greenify or Purify

Nothing wrong with clean master. It's not integrated into Samsungs firmware for nothing

Theres a Battrey Saver Option That Works Like Charm, U Can Find It In Setting/Battrey Look On The Right Side Top Click On Those 3Dots N Turn It On, It Reduces Performance n Data Saveng Extends Battrey Life By exta 3 hrs With Default Powermanagenment Turnd On

the donation package of greenify can hibernate system apps too but it requires the xposed framework.
amplify is also good, it controls wakelocks on your phone (also requires xposed),
and forcedoze (also requires xposed) as the name suggests forces doze to start the instant you lock the phone or the screen times out instead of 30 minutes later...