Hi all, I'm new to fishlore and just started my first fish tank thanks to somone giving me their setup leaving the hobby. It's a 40 gallon with a canister filter. My question is the canister came completely empty (I threw a bunch of ceramic rings in it to get started) what all should i put in the three levels? Also there was only half a sealing ring where the input feed pipe feeds the lower canister when I opened it up it was split and half gone. Do I need to find a replacement seal ring or are they not that critical? Thanks for helping out the noob. Here's a picture of what I've done so far any feedback you can provide would be much appreciated.