Some keys to starting with a moorish idol (based on research and personal experience):
Research the dietary needs of the fish and be prepared with what is needed
These fish require nori and sponge. Have different colors of nori; purple or green, on hand and feed both, your idol is a picky fish and may only eat one and not the other. (Mine will touch green but loves purple.) Foods such as Ocean Nutrition Angel formula frozen cubes contain sponge. Their food should be enriched by adding vitamins such as Selcon.
Buy a healthy specimen which is already eating while at the store
This is important with all fish but even more so with the idol. Out of dozens of local fish stores that I have visited around the bay area there is only one location; Aquatic Collection in Hayward, CA, that actually carries the Moorish Idol on a somewhat regular basis and they seem to know how to care for them while in their care. They should appear parasite free so that means no spots and no scratching against decorations. Always ask for the staff to feed the tank and watch for the fish's feeding response. DO NOT BUY IF THE FISH ISNT EATING. A healthy individual will have a streamer growing from its dorsal fin. Conversely, an exposed spine from the dorsal fin may reveal a fish that is not having its nutritional needs met and should be avoided. Once these fish go downhill, they do not seem to be able to rebound
Add to an established reef system
I've not had success adding this fish straight to QT so I do this first instead. This seems to make sense as the idol is not a fish that adjusts well to aquarium life. In adding to an environment that has micro fauna, sponge and algae growing on live rocks and sand; allows the fish to adjust better to life in your future care rather than a sterile looking world of bare bottom tanks and white PVC pipes. I've kept two idols in a mature "acclimation reef tank" for a month or more with the goal of then transferring to a sterile QT. (I lost one idol after a return pump wasnt turned back on, was in this acclimation tank for nearly 6 months)
Absolutely must QT and treat with Copper and Prazipro for long term success
My "success" with the idol is something I've worked hard (and smart) on for a few years now. I have 1 in my 220 gallon main display for the past 3 months (I know this is a limited time) and it seems to be thriving along with 6 tangs. Tangs, as you may know are a cousin of sorts to the idol in the fish world, that should also be treated with copper and other meds like prazipro to eliminate pesky parasites.
I've successfully treated other fish with a therapeutic level (0.5mg/l) of Cupramine and the same should be done for the idol for 30 days. Regardless of symptoms of parasitic infection, I suggest you do the same, and include Prazipro in your QT treatment as well. I highly recommend you have a Hanna instruments copper checker to ensure that copper doesnt dip below the minimum therapeutic level of 0.35mg/l.
Note: Ionic and chelated copper treatments differ on dosage. Be sure to do your research and make sure your fish is not overly sensitive to a certain copper treatment before use.
I've lost 3 of these fish trying to QT them directly from the store but now have one beautiful, happy, slightly fat idol swimming around my little piece of the reef. The above points made this a reality and I fully expect to have this Moorish Idol for years to come.
It has always been my favorite marine fish and I wasnt going to let failure get the best of me. Learn, get better and try again. Success is rewarding and keeping this fish is one heck of a prize. But please, if you are not willing to prepare and adapt, do not attempt this EXPERT LEVEL FISH.
