fish_tank.rb

class FishTank
  def initialize
    # great place to do any initial
    # setup or configuration
    @fish = []
    @water_volume = 0
    @salinity = nil
  end

  def fill_tank(volume, water_type)
    @water_volume = volume + @water_volume
    @salinity = water_type
  end

  def salinity
    @salinity
  end

  def add_fish(fish)
    @fish << fish
  end

  def count_fish
    @fish.count
  end
end

tank = FishTank.new
puts "made a tank: #{tank}"
puts tank.count_fish