Altosid is not a toxin such as chemical agents. It effects only target pest, and does not horm other organisms in the water and environment. It is even reported by WHO (World Health Organization) that Altosid can be used in drinking water due to its highly secure structure.
After the applicaiton of Altosid, it is not observed an effect on the larvae, and the last instar larvae may be rather larger than the normal. The larvae become pupae normally. Those pupae either die or do not become adult.