If you have parameters before the sand bed vacuum to compare with the after, that might help in pinpointing what’s going on. A big stress on the animals are large fluctuations, temperature swings can definitely affect animals & bio load of the aquarium, putting everything into shock. I’ve seen incidents where the RO water being used for water changes is 6-8 degrees warmer than the aquarium water & after pouring the warmer freshly mixed RO water into the tank, 5 minutes after pour in all coral & inverts went into shock & also affecting the bio load, creating a nutrient swing as well. Double the trouble & it is summer. The ammonia is very suspect & can indicate that either too many nutrients were pulled out or too much died off from some type of shock like temperature or contamination. My 2 cents. Hope that helps & might click something. Good luck.




