hmm, i always read to treat for 6 hours? it seems the medication isnt too harmful to sps(you can dose quite a bit more than reccomended), so i guess double the time wouldnt be too bad.
Eric Borneman has conducted a lot of research in this area, and my interceptor treatment protocol is based on his findings and what my Veterinarian recommends.
Per Borneman, " Treatment dosage appears to be flexible, if not variable. Given the apparent low toxicity to corals even at elevated dosages, [Borneman] suggests a dose level equal or higher (up to 10x) than suggested by Dorton. Dorton suggests three separate treatments of six hours. Upon examination of treated colonies, six hours appears to be insufficient for a 100% kill rate, while 12 hours seems to be more effective. In the one test where coral mortality was observed, the treatment time was only six hours, and in all other tests, no ill effects to the coral were seen with extended treatment times. It appears that time, and not dosage level, is the critical variable towards providing 100% kill rates for the copepods. "