Lovely looking ray. Glad all seems to be fine. Check the Nitrate in the tap water too as mine is 25ppm out the tap. When you say high I imagine it was off the chart at 100ppm+, keep an eye on it as it can be hard to get it down. The tank is not all that large in volume of water and Rays produce about 3 times the ammonia as most other fish so when they defecate it can have a big effect on the water, the fact you are producing a lot of nitrate is good as it means you have effective filtering but the time it takes to convert the ammonia spike can be crucial. It is also worth growing Pothos (devils Ivy) on the tank lid with the roots in the water as these are great when Nitrate is really high, I have found that they don't do as much at under 50ppm but over that they grow like mad which strips the nitrate out of the water.