I use fish emulsion fertilizer that I purchased from my local nursery because we have a marine (salt water) aquarium. I have heard of folks with fresh water fish tanks using the water for their plants but I don't have any direct experience with fresh water tanks so I'm not sure if the water would be an asset or detriment to the plants.
Hopefully someone with fresh water aquariums will pop in and comment.
~ I'm an old gal who still loves playing in the dirt!
~ Playing in the dirt is my therapy ... and I'm in therapy a lot!
Fish water already fertilized also, i don't have enough tanks to water my plants every day whit it.
Many fishbreeders i know use the water for their plants.
If fishwater was bad, no plants would grow in tanks and ponds.