For a tank that size and if it's infested the way you say,.....I'd just startover, yank all the LR out, dip in FW, not soak, but dip then scrub the heck out of it and then rinse with SW.....You could also invest in Berghia Nudibrachs, the only nudi that has a specific diet of aptasia, it's the only thing they eat, would take a while but might work