what you are describing does sound like fish lice and yes they are easily seen by the eye. maybe a salt bath of 3 level teaspoons per gallon for a few minutes might get them off.

as for the algae, what are your nitrate readings? also keep your light on for just 8 hours a day to see if this helps and make sure your tank isnt getting any natural sunlight too. Live plants can help eat up the nitrate so leaving less for algae to feed on. If the temp is low then you could get a hillstream loach to eat the brown algae but only if hes big enough not to be eaten.