During my husbandry internship I had to write a paper on coral husbandry, propagation, nursuries whatnot. Scanning through articles I could cite, I read something about pests and it mentioned using Interceptor. I didn't think much of and continued searching but when I was in the vet room at the aquarium I saw a box of it. I asked the guy I worked under about it and he testified for it. They hadn't had a use for it at the aquarium, but he used to work in a fish store and they used it there to treat for it.
The article I was reading about it is below (link at bottom). I hope this helps. Good luck and let us know how it goes.
Red Bugs (Tegastes acroporanus) have become a global pest species in captivity over the last five years. These copepods have quickly spread across the Acropora sp. keeping world as reefers fragment and swap species freely amongst each other. These “bugs” act as an irritant to Acropora (only known genus they live on) coral, much like fleas or ticks on mammals. Since they have direct development, they can spread fairly quickly. They rarely lead to the death of the coral, but impede growth and polyp extension and can lead to mortality in severe infestations. A coral that starts to lose growth tips, coloration and polyp extension should be searched thoroughly for these pests. A magnifying glass is useful to look over the coral with, as the little yellow copepods with a red dot on their abdomen are then easily seen.
Once an infestation of red bugs has been confirmed, a plan of action is now in order. Some have done nothing and their corals continue to survive. Another course of action is trying biological controls. The usual course of small wrasses, pipefish and symbiotic coral crabs (Trapezia sp.) can be tried. If this course of action is tried, be aware that these copepod predators may keep the numbers in check, but will most likely not eliminate all of them. Because of this, the corals should not be traded or swapped with others. The best way of treating Tegastes is using the heartworm drug Interceptor for large dogs (Milbemycin oxide). The most effective treatment is to use 1 tablet of Interceptor for large dogs per 1,436 liters of water (23 mg Milbemycin oxide per 1,436 L or 0.016 mg.L-1), and add to the tank for five to seven hours. The corals can either be treated in the exhibit system or separately. If treating an exhibit, keep in mind that other crustaceans may be lost during the treatment. Try to remove ornamental crabs and shrimps to avoid losses during the treatment. After the treatment is finished, a small water change and carbon can be added to the system.
The number of treatments can vary from a one time treatment to twice per week for three weeks (six treatments). At the Omaha Zoo both display and propagation systems were first treated with a one time treatment. After a few months, the copepods made a return. The systems were then treated once per week for three weeks (three treatments) and again, they were not eliminated. It was then decided to try the twice per week for three weeks treatment. The copepods were eliminated and have not returned.
As stated earlier, the treatment is fairly benign to corals, but it will affect any animal that has a chitin-based shell such as crab, shrimp and various sand fauna. An attempt should be made to remove symbiotic crabs and ornamental shrimp from the tank before treating. After the end of the treatment, it might be necessary to reintroduce some live sand to get the sand fauna population reestablished.