I agree with EVERYTHING Myka wrote about HA and how to get rid of it.... except the snipping and shaving. I'm way too lazy for that!
I had HA all over my tank, it was horrible, ugly, annoying, everywhere.
My solution was a bit more drastic though but I had overnight success!
I have a 90 gallon tank so I did a 24g W/C. I kept all the old water. I put 12g into two 6 gallon buckets. Then I had 2 -24g rubbermaids with the rest of the water divided between them. I also had a 6g bucket of new water.
What I did was I gathered a bunch of different brushes, nail brush, toothbrush etc...
Then I took out the coral and placed them in one of the rubbermaids. Then I took out every affected rock (HA is usually only on exposed surfaces so the rocks under the top layer were fine) and brushed it vigorously under water in one of the 6g buckets with old water, then I swished it around, then I swished it in the second 6g bucket and then finally in the 6g bucket of clean water, then placed it in the second rubbermaid. Repeat this until you've done all the affected rocks.
Rebuild the tank and voila!
Your tank will be cloudy for a day or so but if you control the rest of the problems, (nittrate, phosphate etc...) it will be the end of the HA!
It's been at least 6 months since I did this and still no sign of HA!
