I have a canister on my 20g. Water stays pristine always. I switched out from HOBs because they let out too much co2
from the water and also got clogged up from all the plant matter I've got too quickly. It's up to you really. The HOB
also kept the water in check but I never liked it's intrusive appearance. Plus, my spray bar helps keep water fully circulated through the tank.
, I'd just save the money and buy lots more live rock and koralia nanos. For the price of a good canister you could probably net 20lbs of live rock and 2 koralias.
edit:+1 for thincat