Gem Tang Diagnosis - (Beginner reefer - thanks!)

[MnFish1]

This is clearly ich. Quarantine still warranted and treatment is a case of sooner the better.
You will need a tank large enough to house the fish you have and leave the display tank fishless for 45-60 days to allow cysts to die off without a host.
Treatment will be preferably copper Power, otherwise coppersafe at therapuetic level 2.25-2.5 for a FULL 30 days at 80 degrees monitored with a reliable copper test kit such as Hanna brand and provide additional oxygen via airtstone. Be sure to monitor ammonia level also with a reliable test kit.

It is not clearly anything without a history - but the treatment is still the same IMHO - Copper - followed by a normal prazipro treatment

 

[Crustaceon]

Get a 20 gallon brute trash can, drop in a heater, an airstone, fill 3/4 with salt water, preferably from the tank to reduce acclimation stress, medicate, add ALL of your fish. Try to get your fish to eat every day. This is EXTREMELY important Garlic fish foods help and I haven't seen too many fish that won't go nuts for live brine shrimp or at least frozen mysis (even tangs). Try to remove any uneaten food from the bottom every day (I wave around a brine shrimp net near the bottom). Check salinity/top off with rodi as need to compensate for evap, replace a few gallons every day with freshly mixed salt water and add copper meds as directed to maintain levels. As noted, you'll want to to keep the display fallow for 45 days to ensure those little ich buggers starve and their little eggs don't have new targets when they hatch. It's not going to be a pretty setup, but it'll work.

 

[Jay Hemdal]

It breaks my heart when I see these issues - the fish certainly have ich, and probably have flukes as well. If the value of the invertebrates in your tank is high, then your only real option is to set up a quarantine system, establish a biofilter, and move all of the fish over. Give them a 5 minute FW dip on the move and then dose them with full coppersafe right away. If you can pull the inverts and put them in another tank, you could treat the main tank with hyposalinity.

No easy way out of this I'm afraid!

Jay