I wouldn't think it would be good except for a fish only tank. Mushrooms may do OK, but a 55gl it kind of tall and PC does not have very good light output. The price of T5s is not high at all for many of the fixtures available and retro kits even less so. This would be the way to go if you are wanting to keep some corals. Besides, the price of replacement PC bulbs is not very good at all IMO. Replace bulbs a couple times and you have purchased a decient T5 outfit.