Old tank water as plant fertilizer? - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 5 Old 07-19-2012, 10:26 AM Thread Starter
KPainter's Avatar
Old tank water as plant fertilizer?

I've heard old tank water from water changes makes good plant fertilizer. Anyone do this? Know anything about it?

-Kristen's tanks:

14g Tall:
Planted, eco-complete, Red Cherry Shrimp

16g Aqueon Bowfront:
Planted, eco-complete, 8 Ember tetras, 7 Green neon tetras, 6 Harlequin Rasboras

36 Aqueon Bowfront: Planted, sand, 10 Julii cories, 8 Zebra Danios
7 Cherry Barbs, Asst snails & Ghost shrimp
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post #2 of 5 Old 07-19-2012, 11:39 AM
Geomancer's Avatar
Old tank water contains Nitrate, which is a form of Nitrogen which plants need. There are also dissolved organics.

I don't hink you could use it exclusively as a fertalizer as it won't have every nutrient needed, but it's better than plain water for plants.
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post #3 of 5 Old 07-19-2012, 12:35 PM
sidluckman's Avatar
Agreed. It will have, at best, only the most mild fertilizing effect, but often it is a bit better conditioned, a trifle softer, and probably of a better temperature than what we usually give our houseplants. Also, it's "thrifty" making excellent use of waste water that really should not be wasted.

In warm months the end of my python aquarium hose goes out the window and into the garden, not down the drain. Tomatoes like it.

thousands have lived without love; not one without water.

W.H. Auden in "First Things First"
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post #4 of 5 Old 07-19-2012, 09:17 PM
thekoimaiden's Avatar
I agree. It's not a comprehensive fert for plants, but it's a great way to get a little bit of extra water and nutrients on plants. It's especially good in a drought if you have watering restrictions or if you're just trying to cut down on water usage. All of my tank water goes to the lawn and garden in the spring and summer.


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post #5 of 5 Old 07-20-2012, 06:22 PM
Byron's Avatar
It works well, as others have mentioned. For many years my houseplants--and I had a lot of them--only got fish tank water and they were remarkable. My Philodendron extended for 14-15 feet when I moved and gave it to friends.

I now use rainwater, no ferts added, on my fewer houseplants, and they respond well to this too.

Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]
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