Dropping the Interceptor bomb

Reef Bass

colors and textures
Saturday was a good day. Thanks to two very helpful vets in town I picked up some Interceptor. I was completely upfront with why I needed it and provided some pictures (you’ve seen them posted here) as “proof of infestation”. I described the treatment course and dosage info I picked up here at RC. The vets totally understood the idea of parasitic arthropods (some types cause mange) and using milbemycin (the active ingredient in Interceptor) to treat them. One even did some online research on their “vetnet” and found corroborating postings for the off label use of milbemycin to treat “Red Acro Bugs”. The treatment course and dosage described there was identical to that described here.

Returning home I mixed up 10 gallons of salt water to replace that with which I filled my new 10 gallon QT setup. The cost of the setup was less than the repurchase price of my crabs and shrimps and I plan to use it again to quarantine new arrivals in the future.

I constructed a shrimp trap with a 2 liter soda bottle.


Sunday morning before dawn I dropped a cube of frozen mysis in it and put it in the tank to attempt to capture my peppermint shrimp before they hid for the day. Within about a minute one peppermint went in. I gave it another 15 minutes or so and when I checked again there were 2 peps in the trap (and 3 nassarius snails), so I pulled it out, transferred the shrimp to the qt tank, rebaited the trap and returned it and the snails to the main tank. While waiting for the fire and cleaner shrimps to volunteer for relocation, I started catching hermit crabs manually and transferring them to the QT tank. Rounded up more than 20!

Five hours after trapping the peps, it was apparent that the cleaner and fire shrimps were not going for the trap. They checked it out but wouldn’t enter. So I picked up my net and went shrimping. Of course I ended up dismantling about a third of the rock in the tank but I caught them.

QT tank with occupants plus some bits of stuff I threw in for them to crawl around and hide behind. They don't get a good grip on the bare glass floor and pretty much skate and slide around.


The good news at that point was that I had my shrimp and crabs out of the kill zone and into the QT tank. The main tank, however, was a shambles. I restored the rock, although it never seems to go back quite the same. An unfortunate consequence of my dismantling rocks was accidentally dislodging four or five corals and unintentional fragging a couple. And of course I was about out of glue, so it was stop everything and go get that. Four tubes later I had everything back in place and the newest frags attached to something.

Both tanks were now set. I used a mortar and pestle to crush an Interceptor tablet and weighed the powder â€"œ 1 gram. One tablet treats 380 gallons or 4 95 gallon treatments. My tank is 100 gallons, which minus rock, sand and coral plus sump water ends up about 95 gallons. I mixed a quarter gram of powder into some warmed reef water and stirred and stirred. At bedtime I poured the medicine around the top of the tank to avoid pouring the concentrate all in one area. I plugged the air intake to my skimmer and let it run for 10 minutes to ensure the med got into it without being bubbled out. Then I unplugged the skimmer and went to bed with the tank running as usual otherwise.

This morning, 8 hours later, I plugged the skimmer back in and performed the water change. I had mixed my replacement water too salty, so after diluting it to where it should have been (before adding it to the tank!) I ended up doing about a 35-40% change.

Here’s a full tank shot now.


Apparently I missed two hermits and a peppermint shrimp. They’re done. QTing the shrimp and crabs was a good idea. Everybody else looks fine. Probably the biggest stressors to the non arthropods were just the usual water change items â€"œ ionic differences between the reef water and the fresh salt water and a temperature drop when the new salt water was introduced. I really should heat my replacement water before adding it.

I have two more treatments to do, each a week apart followed by water changes and then it’s complete. The next two should be basically glorified water changes as with the shrimp and crabs already isolated all I have to do is weigh, mix and add the medicine 6-8 hours before changing the water. Piece of cake. Death to the red bugs!

Reef Bass

colors and textures
Thanks Jeff. I'm pleased that my experience can benefit others. I would reinforce that getting on the problem before it became a crisis, that being upfront with my vet(s), and that it is really all very easy in the grand scheme of things were the key points here.

My failures I would list as not having warmed my replacement / water change salt water and not having QT'd every last desirable arthropod (crab, shrimp). I really did try but a couple them hid for many hours. Oh well. I still saved much $ by qt'ing those I did despite my initial investment in a 10 gallon qt setup.

As a side note, I think the medicine affected bristle worms too. Bristle worms I believe are annelids (segmented worms), not arthropods, though are of course invertebrates. There were a number of overly visible, overly lethargic, overly half emerged from their hidey hole sprawled out on the sand bristle worms that weren't as active nor as engaged as one usually sees any bristle worm that are visible during the day. My hunch is that a sufficient exposure to a sufficent concentation (though probably much greater than that used here) could negatively affect them in a substantial way. They all appeared to recover, or at least stop sprawling out from the holes over the sand bed long enough to retreat back into their holes.

I feel very confident and very pleased that I have dealt with my first round of coral pests. It seems inevitable that there will be more, but I will deal with each as it becomes apparent. My love of reef keeping and satisfaction gained from it so vastly outweighs the hassle of any potential infestation that while I may be temporarily frustrated or saddened, I will overcome.
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Reef Bass

colors and textures
Round two update - Dosed the tank Sunday night and changed 35% of the water Monday morning. Everything went according to plan. Noticed several Devils Armor zoas simulataneously "pooping" mucusy brown stuff earlier this morning. Maybe nothing, maybe a reaction to the medicine or another large water change? Their colors were popping later yesterday (very bright), so they appear happy.

The medicine has not killed all arthropods. I saw some live amphipods today. And dead ones too.

QT tank residents seem ok. That's a lot of shrimp and crabs in a small uninteresting area. I've been doing a 50% water change on the tank twice a week. I mix up 5 gallons of salt water and add to the sump then siphon 5 gallons into the qt tank from the main tank. The HOB biowheel filter has carbon in its filter cartridge which should remove any remaining traces of Interceptor from the incoming tank water.

Final treatment this Sunday and final water change Monday. I haven't seen a red bug since the first treatment.

Reef Bass

colors and textures
Final update - Dosed 3rd and final round of medicine Monday am. Did 30% water change 6 hours later. Friday I did another 30% water change and this morning (Saturday) I put the shrimp and hermits back in the tank.

In summary the treatment was successful and not too difficult. I was able to preserve the vast majority of my shrimps and hermits in the QT tank. And the cost of replacing them would have significantly exceeded the setup cost for the QT tank. Plus now I have a small tank for QT or medication purposes.

I think I could have done a better job splitting the crushed tablet into 4 equal portions by eye than with the scale I used. As a result, I believe 30% more medicine was present in each dose / treatment than the recommmended quantity. On two of the 3 treatments I also soaked the tank for 8 hours instead of the recommended 6. These variances from the prescribed course did not seem to have any negative consequences of which I am aware at this point.

I stand victorious over the (tiny) bodies of my enemy. :p


New member
You only have to treat the tank once, just do a double dose and leave it in the tank for 12 hours.

After the treatment, your nitrate will go way up, 30% water change is good, but keep an eye on it, you might need another 20% water change and run carbons to take out the rest of the med.