It's time to replaster our 23 year old pool. In the past 5 years, black algae has been a problem. Have gotten several quotes to re-plaster. I really want the same solid white plaster that has been used for years but I have been told that the plaster today is not the same formula and that the black algae will come back thru. I have been told that if I plaster, it will only last a couple of years. My old plaster lasted over 20 years and has only started looking bad recently. I really don't like the pebble finishes due to the roughness and the fleck appearance. Any suggestions?