Uses for Fish Tank Water

What do you do with the leftover water from your fish tank maintenance?


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By J.R. (Guest Post)
December 2, 20040 found this helpful
Best Answer

I use it to water my plants. It makes a nice no-burn fertilizer for my herbs. I used to use fish emulsion, but since I became a vegetarian, this has been a humane solution that costs nothing!

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December 2, 20040 found this helpful

Fish tank maintenance requires that you replace a portion of the water on a regular basis. Use that fish tank water to water plants, for the cat's water dish, or pour it in your toilet to flush it. (It takes 2 gal to flush it)

By coolchinchilla

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By Lynne (Guest Post)
December 2, 20040 found this helpful

I don't know that feeding it to the cat is a good idea. There's a lot of nitrogen waste in that water (i.e.


fish poop) that isn't too good for animals in high concentrations. However, plants LOVE this water!

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December 2, 20040 found this helpful

Our goldfish bowl was on the kitchen counter and our cat drank from it for the first 3 years of her life (until the goldfish died.) Because I was always adding fresh water I did not have to change the fish tank water as often as I did before we got Sneaker. Sneaker is now 13 1/2 and I don't think that the water in the fish bowl harmed her at all. I don't think, though, that I would feed any cat the dark smelly residue that is found at the bottom of the fish tank.

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By Linne Dodds (Guest Post)
December 4, 20040 found this helpful

I certainly wouldn't put that stuff in my pets water dishes either but it is great for plants for the same reason it's Not good for pets. It's full of Poop.

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By Jay (Guest Post)
December 6, 20040 found this helpful

Actually if you use the fish tank water for plants you may be inhibiting the plants' growth in the long run. Fish kept in aquariums produce growth inhibiting hormones to keep them from outgrowing their tank. These are also released into the surrounding water and will have the same effect on any plants which receive this water.


When hydroponics first became popular, many people used fish tank efluvia as a growing medium until the efects of these hormones became evident. There was an article on this in one of the back issues of Mother Earth News.

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By Katzprizim (Guest Post)
May 17, 20050 found this helpful

If the fish you have in the tank only get to a certain size like guppies or betas then watering your plants with them won't have any negative effect unless they don't like high amounts of nitrogen. The fish won't be producing any growth stunted hormones to affect your plants. Won't happen if you have fish in tanks that they have more than needed room for growth either. For example lets say that you have 3 oscars about 3 inches each in length in an 80 gal tank with an pleco that was about 10 inches the hormones shouldn't be in that water. Having spent the last 20 years watering various parts of my yard and garden with fish water I haven't seen much of a problem with stunted shrubs.


The hedge closest to my front door is actually larger than the other four. (During the winter I don't care to tote fishy waste water very far in 30 degree temps is what I guess is the reason) My three cats drink out of my tanks but I don't water them with it. I just think it's a bad idea, right there with letting them drink out of the commode bowl. Most of the fish I have are omnivores that I feed goldfish and blanched zucchini to so that could account for it too. Hope this helps you.

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July 29, 20050 found this helpful

I too always use my tank water for my plants. I worked in a pet store that also did this. When the store caught on fire everything died but the plants. I still have some after 10 years. I always said it was from the fish water. I use no chemicals in my tank except for the initial ilimitaion of chlorine.


I never mess with the PH and have no alge. But I wouldn't give it to a cat. It does contain harmful bacteria. I am a cancer survivor and when on chemotherapy I was told not to touch my fish tank. There really are lots of little micro organizems in there that could harm another animal if consumed in quantity.

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