Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
I have heard more about worm castings being acceptable for aquarium use, but mostly not larger animal waste.
Yes, there is a big difference between stall cleanings and manure.
A horse in a stall may have any of many different materials as bedding. (around here, rice hulls and pine shavings are most common)
He urinates in the bedding. He poops on it. He spills water and food onto it.
Then the wet bedding, poop and wasted food (hay) are tossed in a pile to compost.
The high ammonia content (urine) plus the high carbon content (bedding) make this blend compost really fast. Turning it with a tractor, you might get garden ready compost in just a couple of weeks. I think I would compost it longer for possible aquarium use.
Straight manure, perhaps with a little bedding stuck to it, or maybe collected from runs with no bedding will have almost no urine, so the ammonia content is lower. Not zero, though. Horse digestion is not very efficient, and if they are fed high protein foods (alfalfa, grains) there will be plenty of ammonia to blend with the high carbon (dried grass) part of the manure.