I just aquired a pair of curviceps. Really cool fish. My question regards temperature. They are going into a tank that contains a school of cardinal tetras. The temp is kept at 81 degrees. My heater for whatever reason has broad intervals. Meaning one notch lower and it drops to 77. The higher temp has served me well with the cardinals, versus the lower. With that said is 81 too warm for these guys? Thanks.