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[APD] Re: Too many plants??
> Date: Mon, 20 Sep 2004 13:48:35 -0500
> From: "Kevin Sheller" <kevmo at aplants_com>
I didn't see much information relating to water circulation in your tank.
Aside from oxygen generated by plants when they are photosynthesizing
strongly, the only other source of oxygen is diffusion from the atmosphere
at the water surface. If you have poor water circulation, there will be an
oxygen gradient from the top of the tank to the bottom with water on the
bottom being low in oxygen. This is why fish gasp at the surface - they
aren't sucking in air, they are going for the most oxygen-enriched water.
Of course, certain fish DO suck in air but that's a different story.
IMHO, if you have good water circulation, you will never see an oxygen
problem unless you are doing something really extreme (like a tank stuffed
with minnows and water grass).
What type of filtration are you using? Is there strong water movement in
the tank? I'm betting that your only problem is a lack of water movement.
When lights are on, plants are making up for poor movement of oxygen rich
surface water to other parts of the tank. At night, you have the problem.
When you run an airstone in your tank, you're not really "pumping oxygen
in". The bubbles don't stay in contact with the water long enough to do
much good. But they do cause water movement which gets surface water
mixed into the rest of the tank. In a heavily planted tank, the plants may
prevent good circulation from a simple source like an airstone and may
require multiple powerheads or canister filters.
If you use calcium carbonate or sodium bicarbonate to add GH or KH to the
water, the temporary cloudiness that results gives you as good indication
of water movement. If you can add it to your filter, how fast does it
disperse throughout the tank? If you can't add it to your filter, mix it
in a cup first and pour it in one spot in the tank. How well does it
George Booth in Ft. Collins, CO (gbooth at frii dot com)
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