below is a great post by Mark A. Stone.
remember to search google before asking
and HITH = Hole in the Head

Bob
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HITH is, as you noticed, a disease that most experts seem dumbfounded
about. There is very little correlation or agreement on HITH's cause and
cure. However, there are certain things that are almost always common in
an aquarium with a HITH outbreak, and people that treat those particular
things generally (with some exceptions) see their fish recover. These
things a

--Lack of a varied diet, and a lack of plant materials and vitamin C in
the diet.

--The Hexamita protozoan. This is the biggest point at which the experts
disagree: Is Hexamita (which is ALWAYS in the lesions) the cause of HITH,
or is it infecting the lesions AFTER the disease strikes? The medication
you are using should be OK.

--Activated Carbon in the filter.

--An excess of Nitrate, the final product of the ammonia/nitrite/nitrate
process. Frequent water changes and live plants can keep nitrate in check.

--Poor water conditions and high stress. Is the aquarium next to a loud
stereo or slamming doors? Are there smokers in your home?

If you concentrate on the above points, not forgetting to remove the
activated carbon from your filter, you may see some improvement. Visit
the OSCAR Study Page (http://www.geocities.com/Heartland/Pointe/9202) for
a more detailed discussion. And, good luck!

--Mark

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The OSCAR Study Page is at: http://www.geocities.com/Heartland/Pointe/9202
Mark A. Stone
The ".Edu" meens i are smart.