Please help! I got my 29 gallon tank at the beginning of June. I put 2 black moors and a pleco in the tank. After 2-3 days, the pleco disappeared. I figured he was so small the the black moors munched him. On June 18 I bought another pleco. After 2-3 days of being in the tank, my smaller black moor began hiding in a decoration. I routinely check ph, kh, gh, nitrates and nitrites. They have always been at good levels. As of about 4-5 days ago, both black moors are now hiding, I have to lift the decoration and force them out. The smaller one immediately goes back in the decoration. The bigger one will swim around a bit then go back in. I was told black moors were cold water fish but was recently told by Tetra that they need warmer water so I raised the temp to 76.8F. Just a bit ago, I removed the decoration and did a 1/3 water change. I am using SmartStart, AquaSafe and Easy Balance. While doing the water change, I noticed an unusual abnormality on my bigger black moor. It looks like off white colored sand near the beginning of his tail fin. Neither is as velvety black as they used to be. I was treating tank with Lifeguard however Tetra advised me to stop as black moors are scaleless fish. Someone please help me save my fish. I have a picture of the spot on my little baby and a picture of what he looked like a week ago if it is helpful. You may need to zoom in on the picture to see the area of the abnormality. I have also included a picture of my tank setup. Please note, I removed the two decorations on the right side of the tank ( the house and barrel) as well as the large plant on the right.