Water depth plays a big part in how much light the plants need. The LPS by me that I rate a 9 on a 1-10 scale is owned/operated by an ex school biology
teacher. He regularly points out that all his 55 gallon tanks have regular T8 lights on them and the plants do just fine. But he is referring to the two bulb
shop light type fixtures and not which kind of bulbs he uses. I'll check on that the next time I'm there.
For a 55 I would start/w one Zoo Med Flora Sun max plant growth bulb and one 10,000K.
I have the T8 (but on a ten gal) and I like those because the fixtures are one bulb. They can be on separate timers that way. I have one (a Zoo Med Flora grow)
on from 9A till 6P in summer. The other bulb is a Zoo Med Ultra Sun 6500K and it is on from 11A till 3P in the summer. You likely would not think that two of
the Zoo Med Flora Grow bulbs are enough visible light for your viewing the tank. An option for a less expensive one is the Aqueon Full Spectrum (8000K) but
it has substantially less light(visible) than the 10,000K but may be a suitable alternative to the ZM Flora Grow as it advertises it has good plant light.
With two bulbs in a T5 set you will need to limit your light to 7 hrs to keep down the algae. Really any two bulb fixture because you can't regulate each bulb.
BTW: I don't remember where, likely in a review of a bulb, but I read recently that a person said he had tried the 10,000K (it was a T5 and I presume it
was a two bulb set) and found that he got better plant growth/w the 6700K bulbs. As far as I know only Coral Life Nutra Grow comes in 6700K in a T8.
Have never tried one of those as "if it works then don't mess/w it" is keeping me buying the ZM Flora Grow 6500K. My "other bulb" changes from time to
time but that one stays.
Zoo Med AquaSun T-5 HO Double Light Linear Fluorescent Hood at PETCO