I've tried many different filters over the years, Krafty, HOBs and Canisters, and both types have advantages and disadvantages.
But you're running a discus tank, and ime you can't beat HOB's to do the necessary job of maintaining the water quality and conditions you (ideally) want for your discus. They're much easier to keep an eye on to ensure they're operating efficiently, much easier to clean-up/rinse media, & (frequently) keep clean, and are generally better for changing up and varying your filter media for best results in a discus tank.
They also do a better job, ime, of oxygenating & circulating the water, and provide more than sufficient surface agitation to prevent shedded discus' slime coatings from accumulating on the water surface.
(They'll collect on the glass walls and are easily removed with each wc & tank wipe down).
A lot of discus-keepers I have known have gotten lulled into a false sense of security using canisters, as they tended to clean/maintain them less frequently than an HOB, thus inviting less than ideal water conditions.
A lot of these discus-keepers have now abandoned canisters for HOBs.
I have run 2 AquaClear 110's on my 75 gal discus tank for several years, and wouldn't be without them.
AC's are the best HOB's in the business, and I highly recommend you consider this avenue - 2 AC 70's on your 55 gal should do a marvelous job.
That's my .02
Please tell me what UV and tannins are? As I am sure you can tell by my ? that I am fairly new (about a 6 months) and have lots to learn.
