Save your money, don`t get a canister.
Save some time and grief, don`t try to build a denitrator or algae scrubber.
The canister won`t do a thing to help with nitrate levels. It will make filter cleaning a whole lot more interesting.
All that gunk you have been banging out of your simple to clean HOB will be hidden away in a hard to clean container.
What most posts on denitrators and such fail to mention is the long lag time between putting them in service and seeing any results.
Often the results are very disappointing compared to the time put into it.
Up to you.