Hi, I'm sorry but I can't help with what u can use, only with one plant u can't use, and that is willow, willow will make ur fish sleepy, we used to use it for a terrier pup when busy doing monthly accounts etc, we used to give him willow sticks (willow sticks with the bark attached) to chew, there is more tannic acid in bark than leaves,
But research each plant u intend to use.
Also look up bark tanning of hides, cause those guys know what has the higher levels of tannic acic, but u can't poison a hide cause the animal is already dead,, so still reasearch each plant, if u do want to use bark.