No, you don't want to start an algae cycle. Yes, unneeded phosphates and nitrates are a bad thing. After cycling, water changes are usually done, however, once you have nitrates and phosphates, you're already feeding the algae. Once the phosphates get absorbed in your live rock, live sand and such, water changes won't get rid of them. Nitrates and phosphates are natural fertilizers and will do nothing but feed algae. They won't help with a cycle at all. The whole idea of cycling your tank has to do with building up the biological filtration, which has nothing to do with algae. It's about your tanks ability to break down waste products from toxic levels to harmless levels. The more you can do to limit food for algae, the better IMO. Most of the maintenance we do with our tanks is to reduce nitrates via skimming and water changes. Why start out by adding them, when it's so easy to eliminate that part of the equation by using RO/DI water? It's a very low cost, considering all the other equipment we pay for, and the high cost in possible equipment and definite labor you'll spend later to remove nitrates and phosphates.