Is this hole in the head?

[jmadden93]

I've been running my 125gal salt water tank for about 5 months (using dechlorinated tap water), and am now switching to RO/DI water.

My butterfly now has this skin deterioration above his head. Nitrite & Ammonia levels are low... I haven't tested for NitrATE yet, but I did a 10% water change two weeks ago and about once a month before that.

Any idea what this illness is and how i can treat it? This butterfly & my foxface are my only medium sized fish. I have about 5 other small fish so the tank isn't stocked heavily. My SG is 1.019 and has been that way for a few months as I don't have coral.

Any advice, input would be greatly appreciated!

[leebca]

This may have begun a MHLLE, but I think it has gotten to the point of a topical bacterial infection.

In order of what I think is most likely the cause(s) of MHLLE:
Vitamin deficiency (A and/or C); Poor Nutrition (including underfed and wrong foods)
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)
Retrovirus
Hexamita
Amyloodinium-like dinoflagallate
Stray Voltage (is your system grounded properly?) [the article below disagrees with this one]

See this article for more info on MHLLE:
Marine Head & Lateral Line Erosion: A Description of the Syndrome and a Review of its Speculated Causes by Steven Pro - Reefkeeping.com

If MHLLE began this, then the bacteria are taking over. Between the bacterial infection and MHLLE the common causes are nutrition and stressors.

I'd move the fish to a quarantine tank, treat with a topical antibiotic for saltwater fishes, and improve its diet. You need to read this as to the choice of foods AND the use of vitamin and fat food supplements: Feeding Marine Fish and Fish Nutrition

For a choice of antibiotic, I would go with NITROFURAZONE (in the product, Furan-2) or KANAMYCIN (in Spectrogram).