Head and Lateral Line Erosion
Researched and written by Nathan Henderson
Q: What is Hole-in-the-head/head and lateral line erosion?
A: Hole-in-the-head (HITH) and Head and Lateral Line Erosion (HLLE)
are two terms for the same problem--skin de-pigmentation and the formation
of holes, ranging from pin-hole sized to large craters, in the head and
along the lateral line of fish. A small 'hole' in the head doesn't always
mean HLLE though--the fish most commonly affected have small pores in their
face area naturally--if you aren't sure, compare the size and location
of the 'hole' to other fish. If it's the same on all fish or on both sides
of the fish's head, it's probably nothing to worry about, but even this
can be difficult to judge since the holes often appear in the same locations
on different affected fish. As such, a good familiarity with your fish
and/or a good picture of a healthy fish can be valuable for diagnosis.
Freshwater HLLE is most commonly found in the larger South American cichlids,
particularly discus, oscars, and Geophagus species.
Q: Is HLLE dangerous to my fish?
A: HLLE is a chronic disease, meaning that it's presence is not fatal
in the short term. However, affected fish can eventually become anorexic
and lethargic, and the open wounds can easily become the source of secondary
bacterial and fungal infections.
(1) E. Noga speculates that these secondary infections may be the ultimate
cause of death in fish with HLLE. Although it is not normally immediately
fatal, HLLE should be treated as soon as possible, both for the fish's
health and to prevent permenant disfigurement of your pet fish. (Small
holes at least can heal fairly quickly, but very large holes may take months
to heal or never heal completely at all.)
Q: What causes HLLE?
A: Nobody knows. There is not enough research to authoritatively say
what causes HLLE, however, there are several theories:
HEXAMITA SPECIES: These flagellates can cause problems in tropical fish,
but their association with HLLE is not conclusive. It is suggested that
they may spread through the fish's system, causing damage directly (1),
or interfere with absorption of nutrients, with the malnutrition of the
fish being the actual cause of HLLE. (2) In favor of this theory is the
presence of Hexamita in many fish with HLLE, and that treating with anti-hexamita
medications is often effective against HLLE. However, cases of HLLE with
no Hexamita present indicate that while Hexamita may be one cause of HLLE,
it is apparently not the cause in all cases.
THE CALCIUM/PHOSPHORUS DEFICIENCY THEORY: HLLE may be the result of
deficiencies in these minerals. This theory is supported by low levels
of calcium/phosphorus in affected fish and reports of adding calcium/phosphorus
supplements being beneficial to the recovery of fish with HLLE. It is suggested
that the deficiency is caused by an infestation of Hexamita interfering
with absorption of nutrients. (2) That most flake and pellet foods provide
a great deal of both minerals, yet HLLE occurs in fish on such diets suggests
that other factors are involved (listed in the other theories) that interfere
with the absorption and/or utilization of these minerals.
VITAMIN C DEFICIENCY: It has been noted that adding vitamin C can aid
in the recovery of fish suffering from HLLE, leading to speculation that
lack of vitamin C is the original cause of the disease. While vitamin C
is very important to the immune system and the healing of wounds, fish
fed vitamin C deficient diets show no signs of HLLE but do show deformities
in HLLE affected fish. (3) Because it is such an important vitamin
in the recovery from illness and wounds, adding a vitamin C supplement
to the food of fish being treated for HLLE is recommended. Fish fed large
doses of vitamin C have still developed HLLE (5), so the mere presence
of C in the diet doesn't appear to offer protection from HLLE, although
it still has other benefits.
VITAMIN D DEFICIENCY: Insufficient levels of vitamin D have also been
proposed as the cause of HLLE. This theory has a certain 'neatness' to
it, as vitamin D has been identified as the precursor to a hormone important
in maintaining levels of calcium and phosphorus in the blood and bones
(3) which explains low levels of both minerals in affected fish. In support
of this theory are reports that adding D to the diet of fish with HLLE
is beneficial (2), as well as observations that exposure to ultraviolet
light (which is used to manufacture D in the fish's skin) may be beneficial.
(4) Since little vitamin D is found in most ingredients of fish foods,
vitamin D should be added as a supplement in most commercial fish foods.
(3) Like vitamin C, however, HLLE has NOT been produced in the laboratory
as a result of feeding vitamin D deficient diets.
THE STRESS THEORY: HLLE has also often been associated with poor tank
maintenance, and been suggested as a reaction to constant stress. (1) This
might occur as a result of higher nutritional needs while under stress
not being met, or by simply weakening the fish to the point where they
are vulnerable to infections like Hexamita (or other unidentified pathogens.)
personal experience supports the association with poor water conditions,
although anecdotal evidence should always be treated with some skepticism.
THE CARBON THEORIES: There are several theories that the use of activated
carbon in tanks may cause HLLE.
One version of this theory is that the carbon could be causing nutritional
deficiencies by adsorbing vitamins or trace minerals either directly from
the water, or by adsorbing molecules that the needed nutrients could then
bind to. This theory, however, has several problems: There aren't any vitamins
in tap water to begin with, and minerals like calcium, phosphorus, and
iron should be available in large quantities in most prepared fish foods.
Additionally, it is reported that fish rely on food for nutrients, trace
and otherwise, making the presence of nutrients in the water irrelevant
(4) although fish have been shown to be able to extract various minerals
from the water (calcium, iron, zinc, etc.)
A second carbon theory is that some types of carbon may release toxins
which cause HLLE. Perhaps a more specific variant of this theory is that
some poorly manufactured carbons might release chemicals that cause stress
to the fish. (See THE STRESS THEORY.) Another theory is that loose particles
of carbon dust in the water have some caustic affect, but there is no support
for this that I have been able to find.
All carbon-related theories regarding the cause of HLLE suffer from
one other significant shortcoming: HLLE can be found in tanks which have
never had carbon of any sort used in them, yet is NOT found in many tanks
using carbon. While it remains possible that carbon may be involved in
some cases, there is no reason to believe it is a factor in most cases,
if any. There is no sound evidence for a link, or even a logical specific
theory--at best, the carbon-HLLE theories amount to a handful of individual
cases where HLLE was seen in tanks using carbon, but appeared to improve
after the carbon was removed. Since there is little to no information on
what other steps where taken in the treatment of the HLLE, the association
with carbon is rather suspect.
ASSORTED THEORIES: Electrical currents in the tank, a virus, and a few
other factors have also been suggested as causes of HLLE. No data available
on their likelihood as a cause.
Q: How do I treat HITH/HLLE?
A: Lacking a solid answer as to what causes it in the first place, I
would recommend all of the following:
1. Keep the tank as clean as possible. The water should be clear and
not smell, and the bottom should be regularly cleaned, with frequent water
changes (and I do mean frequent--at least every few days or even daily.)
If your tank is anything less than the ideal environment, it's time to
get religion. Try to provide as clean and stress-free an environment as
possible at all times, not just when your fish actually get sick. (Regardless
of the role of water quality in HLLE, I would urge everyone to keep their
tanks as clean as they can--there are many problems that are definitely
caused by poor water quality and can be prevented simply by doing regular
2. Treat for Hexamita. Given the frequent association of Hexamita with
HLLE, this seems like a prudent step to take, and if nothing else, it can
help with other infections possibly present. Indeed, many (most?) cases
of HLLE seem to respond to Metronidazole. (Metronidazole is used in most
hole-in-the-head medications or can be readily found in common anti-protazoan
medications like Paragon II.) Also suggested are giving magnesium sulfate
(Epsom salts) orally, and raising the tank temperature to 95F (35 C) for
seven days. (1) Many commercial products like Hex-a-mit contain Metronidazole,
or it is available under the name "Flagyl" to pharmacists and veterinarians.
Thanks to Jeff (firstname.lastname@example.org) for contributing the following on medications
"Metronidazole is the preferred medication. It is the same medication
found in Hexamit. It is also found as one of the ingredients in Paragon
II. Dr. Axelrods Mini Atlas recommends 100mg metronidazole per 10 gallons
every other day for 3 treatments (and the dose can be safely doubled).
Hexamit recommends 250mg per 10 gallons with the same time schedule. I
found that the 100mg was not effective but the 250 was. Some recommend
3 consecutive treaments rather than every other day (have not tried it).
Metronidazole is a commonly available medication at any pharmacy or
vet, so contact your vet (if you have one) and get a prescription--it will
be a fraction of the price than buying it mail order or from the local
aquarium shop. 250 mg Capsules or tablets work fine (Capsules--empty them;
tablets--simply dissolve in warm water).
Metronidazole in food. The Axelrod mini atlas recommends 100mg of metronidazole
mixed with 1 tablespoon of food. The food could be beefheart (then refrozen
in small servings) or a paste of dry food and water (then frozen into small
Treatment should include both food (if they are eating) and in the water.
I feed them the food for 7 days.
Paragon II is also effective and expensive. Follow the directions on
the package--it recommends the "every other day for 3 treatments" method.
I found that it disturbed the biological balance in the tank (even though
it claims it won't) resulting in elevated ammonia levels and sluggishnish
in the fish. It does work quite effectively against HLLE, but be careful
with this medication- reduce feeding and check ammonia levels daily.
There are also dips to treat HLLE--never tried it but they are supposed
to be very effective if you can get our fish out of the tank and into another
container for a while. (I'd like to hear more in this area, too.)"
3. Add vitamin supplements to the food. Since calcium and potassium
should already be well supplied by most dry foods, adding vitamin C and
D is probably a higher priority. (And don't go overboard with it! Overdosing
fish with vitamins isn't good for them either.)
Odds and ends: Giving the fish a tank that receives direct sunlight
or has full spectrum/actinic lights for synthesis of vitamin D MAY help,
though I haven't seen much on this. Carbon should be removed from filters
if medication is being used so it does not adsorb the medication. Given
the lack of support for the proposed carbon-HLLE link, I don't see any
sound reason to stop
using carbon as a routine practice.
1. "Fish Disease--Diagnosis and Treatment", Edward Noga, published by
Mosby-Year Book, Inc., 1996.
2. "Discus Health", Untergasser, TFH Publications, 1991.
3. "Nutrition and Feeding of Fish", Tom Lovell, published by Van
Nostrand Reinhold, 1989
4. Leo Morin (Seachem), personal communications. (10/96)
5. Nathanael Henderson, unpublished data.
Copyright Nathan Henderson (email@example.com),
This article originated at http://www.pconline.com/~jude/hlle.html#whatis