HOMEBREW HOLDING TANK DEODORIZERS
Here are two "homebrew" holding tank solutions to reduce or eliminate holding tank odors.
1 c ammonia, 1 c PineSol, 1c fabric softener, ½ box baking soda (8 oz).
Put in gallon jug, fill with water.   Use two cups for 50 gal holding tank.
Equal amounts Arm & Hammer soda and Borax.   Do not use baking soda or soda with detergent in it.   Use only pure soda, usually on the bottom shelf.