Head and Lateral Line Erosion (HLLE) in Marine Fish
Head and lateral line erosion is a disfiguring but rarely fatal skin condition of marine fish such as tangs and angelfish. Learn its clinical signs, the multifactorial causes linked to activated carbon and suboptimal husbandry, and the management steps reported in the veterinary literature.
What HLLE is
Head and lateral line erosion (HLLE), also called lateral line depigmentation (LLD), is an idiopathic, multifactorial skin condition rather than a single pathogen. It begins as small pits of receding epithelium around the head and along the lateral line, sometimes extending onto the unpaired fins. It is disfiguring but rarely fatal.
Which fish are affected
At least 20 fish families have developed HLLE in captivity, with severity varying by species. Tangs and surgeonfish are a flagship susceptible group: lateral line depigmentation is a common condition in managed saltwater fish and has been documented in acanthurids, including the palette surgeonfish (blue tang, Paracanthurus hepatus).
Suspected causes
The cause is not fully established. A veterinary review concludes that lateral line depigmentation should be considered a clinical observation indicative of a dermatologic response to suboptimal conditions — that is, multifactorial and environmental. Two studies have separately pointed to the use of activated carbon in closed aquarium systems as a contributing factor.
Management
- Remove all activated carbon from the system.
- Perform large water changes; studies note that greater than 90% may be needed to reduce the effects of activated carbon.
- Consider moving the fish to a system with no prior history of HLLE (source control).
- Correct underlying husbandry with stable, high water quality and a varied diet.
- Discuss topical veterinary options with an aquatic vet; becaplermin 0.01% gel and naltrexone 0.04% have been reported to improve lesions in small studies.
Sources: en.wikipedia.org (Wikipedia, CC BY-SA 4.0); pubmed.ncbi.nlm.nih.gov ; pubmed.ncbi.nlm.nih.gov