I've had a pair for about a year and a half. I drip acclimated them when I got them and clean the filter and do a 75% water change weekly. This helps to keep the ammonia and nitrites at 0 and the nitrates around 10 or less. When filling the tank back up, 1/3 of the water I add is RODI water. This helps keep the water a bit soft (TDS < 250 ppm) and helps maintain the pH around 6.5, as Ohio water is very hard. Rays can do fine at a pH of 7 in harder water but in nature the water they live in is around a pH of 6-6.75. I also keep the temp around 79*F. These water parameters are fairly easy to maintain and the rays seem happy with an incredible appetite.