Welcome to the hobby! :)
I have one of those filters in a 2.5g. It seems to work fine as a filter but I don't know if it would be ideal for a 5.5g. Generally you want equal or more filtration per gallon, but with bettas I'm not sure since they prefer very slow current. Hopefully someone with more experience with the concept will respond.
In terms of water movement, bettas have very delicate fins and are slow swimmers so they like the water to have very little current. I achieved this in my tanks using an air pump control valve and adjusting the flow until the filter gave as much filtration as possible but the betta wasn't forced down by the output of the filter if he swam under it. It took a bit to get the perfect balance but I feel it was worth it.
Last edited by CopperBell; 09-29-2014 at 07:30 PM.