Matt Wittenrich wrote a great book that I got when I had a pair of yellow head sleeper gobies that spawned every 13-14 days like clockwork until the male died of breeding stress and the female bugged out when he was gone and soon followed into the great abyss. In the wild those only live 2-3 years. Mine were with me almost two. I tried like hell to get those larvae past day 4 about 9 times and gave up. Rotifers were not a good first food I think. I even examined larvae via microscope to see if they had food in the gut. Never saw much. His book suggests exactly that, slow trickle from a mature sump on a well filtered system that is much larger, slowly introducing clean water. The larger the larval tank the better. Lit during daylight but not intensely and you can add cultured phytoplankton to remove some ammonia. Round tanks are better. I used a plastic half whiskey barrel liner with a pvc standpipe I installed in the center. Lined the top with very fine nitex mesh. Water volume is the larvae’s best friend. The bigger the better. What species are you trying? That Wittenrich book covers most of what is available today captive reared except some recent success with Tangs and Angels.