My ancestors once taught the settlers of a new land e.ventually to become known as the USA to put fish in the ground under their corn for a better. Harvest. ISN'T IT STRANGE how some times the old ways can get forgotten or become obsolete as technology and knowledge increase to find out later on down the line the old ways. Are still truly more efficient. Or effective. Or better for the environment. 

Another great addition to your garden is the water from an aquarium.
Dip out the well diluted fertilizer water and add more clean water for your plants. I use it on my houseplants too.
Then add clear water to the aquarium slowly to not disturb the fish. Make sure the temperature of the new water is comparable to the old. Repeat as the water gets cloudy.
The plants and the fish will benefit and you won't be throwing away a valuable resource.