hello; I have been using a 4 foot LED shop light on my 55 gallon planted tank for over a year now. It cost o more than $35. A 55 is just 4 feet long so it fits.
I had the lids already which had 18 inch fluorescent tubes. These worked well also but the bulbs needed replacement fairly often.
As johnnyhyde stated look for lumens and I also like the light in the 5000 + K range.
View attachment 1329309
Hello; I think this picture was taken when the 55 had LED screw in bulbs. I had taken the 18 inch fluorescent tube's guts out and replaced them with standard screw in bulb bases. The screw in LED bulbs work just fine and there are now a variety of LED bulbs to choose from.