"The problem is I am overstocked"......or is it under-filtration. You didn't state your total tank stock list or what filter(s) you had on your aquarium. Sounds like you need to add more biological filtration to the mix via an additional canister filter, Hang on the back,etc (I suggest emperor 280 or better a 400 if it will fit). Ate the same time don't turn the tank into a whirlpool as the angels like calm water. Gravel vac the detritus out of your tank EVERY water change if you aren't. If you ever have any questions I can help with feel free to call me. Liquid Therapy Aquarium Service (727)-242-1464