Neil,
You need to be very sure of your diagnoses. Otherwise you could spend time, effort, and money not helping your fishes and end up doing them a disservice in the long run. So first, be sure of your diagnosis.
The HLLE or what I prefer to call MHLLE is most likely causing those patches you see. Read more about this from here:
http://reefkeeping.com/issues/2005-06/sp/index.htm
In order of what I think is most likely to cause MHLLE:
Vitamin deficiency (A and/or C); Poor Nutrition; see this reference:
http://www.reefcentral.com/forums/showthread.php?s=&threadid=785228
Chronic Stress
Poor water quality (including high levels of dissolved organic matter and/or nitrate)
Activated carbon (either removing something the fish need or the dust clogging the pores on the fish)
Stray Voltage (is your system grounded properly?)
Retrovirus
Hexamita
Amyloodinium-like dinoflagallate
If the other is truly Marine Ich (
Cryptocaryon irritans) then you have a few options for treatment as outlined in this two-part article:
Steven Proââ"šÂ¬Ã¢"žÂ¢s article on Marine Ich (Part 1):
http://reefkeeping.com/issues/2003-08/sp/index.htm
(Part 2):
http://reefkeeping.com/issues/2003-10/sp/feature/index.htm
Since two tangs are involved, I'd remove all fish to a hospital tank and proceed with a hyposalinity treatment of a salinity between 11ppt and 12ppt. Watch for pH problems and maintain water quality and pH during the treatment.
Good luck! :rollface:
