Why not? just inspect it well. And try to limit your purchases to recently dated filters.Also try your best to see them running first of course. Canisters are a lot more durable than HOB filters. They have the impeller last rather than first in their water column. I am not sure if all canisters are this way but most are in my experience someone please correct me if I am wrong here.
Honestly, I can usually only afford used canisters. I can't help it with some of the killer CL deals in my area. The most important thing IMO besides making sure it is not 10 years old or in poor working condition is making sure the proper media and hose length that fit YOUR setup come with it. Depending on the model, it can cost nearly the same to fill a used canister as it can to but new.
An Eheim 2217 I bought empty with hoses too short made me reconsider doing the used can thing again not too long ago...
the only canister im running at the moment was used.. i knew what was wrong with it before i got it... it basicly came down to 20 minutes of my time and some silicone... to me it was worth it.. even if it dies it was cheap so im not going to stress it
Leaking gaskets can be replaced. I have a fluval 303 that is 25 years old. it is still going strong. I use it as a vacuum for my pond. Leaking gaskets: Clean the gasket with warm soapy water, then lube with vaseline. works for me every time. another tip, sponge media for filters. buy two sets. If they get clogged. let it dry out for a few days. then ring the sponged out. this breaks up all the dry matter and it falls out. I also vacuum them just to make sure. This improves the filter output.
Leaking gaskets can be replaced. I have a fluval 303 that is 25 years old. it is still going strong. I use it as a vacuum for my pond. Leaking gaskets: Clean the gasket with warm soapy water, then lube with vaseline. works for me every time. another tip, sponge media for filters. buy two sets. If they get clogged. let it dry out for a few days. then ring the sponged out. this breaks up all the dry matter and it falls out. I also vacuum them just to make sure. This improves the filter output.