With all due respect, lawnmower blennies are perfect for a new tank & it's algae issues. & a diamond goby is good in anything over 30 gallons. Years ago I kept both in a 35gal newly cycled tank just fine.
I also disagree. Thought the same as you and got a LMB for my 55 that had been setup for 3 months. Ate all of the hair algae then slowly starved to death. Never touched any prepared foods. They need a larger, established tank IMO.
A good first fish is the lawnmower blennie. They're not too pretty, but will mow down algae on the rocks; & they're very peaceful. Or a diamond goby to keep sandbed aerated. Good luck & welcome to Reef Central.