Canister filter ??
 

I left my canister filter (fluval 405) full of water but not running for the last week as I wasn't sure I was going to keep this tank running. The water level was low as i moved quite a bit when i transferred everything to my other tank. I did keep the power heads going, still snails, crabs and a couple of corals and lr. Now that we've decided to keep it going, I've filled the tank back up (was down about 1/3), I opened the canister and it does not smell good. I had just changed all the media and cleaned it 2 weeks ago, so my question is should I change everything again, or just give it a good cleaning?

Just give it a good cleaning. FYI, if you turn your canister filter off for longer than 30 minutes, the majority of all that good bacteria is pretty much dead.

Why not leave it off?

Good idea and I may be able to eventually. I was running a tunze 9011 skimmer on this tank as well, but I'm sending it back as it's not working, so I would have Nothing other than the lr for filtration. I was thinking of leaving the skimmer off as it wasn't doing much and the tank was running fine.