I wouldn't do a 5 gallon water change in a 14 gallon tank. Our tanks don't like quick changes and that much of a change could do more harm than good. Have you tried chemi-pure elite? 2 or 3 months ago I was trying to get my tank back on track and the biggest hurdle I had was hair algae. I purchased the chemi-pure elite and along with my clean up crew that I had in the tank it really took care of the algae.