This I learned when we visited my husband's cousin who has several big aquariums. The aquariums are being cleaned and my husband, upon seeing the unhealthy plants in the garden, said that the aquarium water is best for the plants instead of being thrown in the sewage. The cousin was surprised because he does the cleaning like that and didn't know that his garden would benefit from the aquarium water. Honestly, I also didn't know about it. My husband added that in some vegetable farms, they have a fish pond more for the water and not for the fish.