The camera is a D90 and I am using an upgraded external flash so I think I just need to adjust the setting on the camera. I am a complete Noob so these are much better for me LOL
do you have any light above the tank? try and get the flash off the camera with an off camera shoe to get light from a different direction. if you have lights above the tank, turn the rest of the lights in the room off and dont use the flash