I had the same problem but had my tank sectioned and dats were in side with no filtration/current. I had 1 of 5 die possibly cuz I turned up the temp. to 87 in hopes of curring pre maturely diagnosed ich. strupid me. added to more and put em in whole 90 gallons. once frozen bloodworms wit current all were eating. after a week fish are even foreging on the bottom for food(especially at night. I also added tetra and after a night my 1 inch dats ate 12-15 glow tetra. the tetra seem to make the dats less timmid and it is cool watchin the dats stalk their pray good luck possibly buy a powerhead to push water (although I turned down output from filter nbecause it was really strong and now they thrive )or add more dats that are strong. eating dats make skitish dats eat