I am having a dilemma with my 29 gallon community tank. Up to this point this tank had been going very well. I aquired 6 marble hatchetfish a couple weeks ago and within a few days 4 had died. The 2 remaining ones are doing quite well and look great BUT I now within three days have lost almost all of my ten neon tetras that I have had for at least 6 months. They are just dying off several a day. I noticed one of the two remaining ones has white cottony stuff on its head like ich. That is the only one that has shown any evidence of any disease before just dying. Do you have any idea what could be happening? Any suggestions for treatment? I now only have 2 young angelfish (that look and act fine), the 2 hatchetfish, 3 three-lined corys and 1 oto cat (I intended to add more otos soon) and a mess of cherry shrimp. This tank is heavily planted and all my water perimeters are fine. I am afraid if this is neon disease I have read about, the entire tank is doomed.