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Re: Light on substrate in 70 and 75 gallon tanks

> Date: Mon, 11 Sep 2000 09:10:46 -0500
> From: James Purchase
> ...A deeper tank will NOT provide you with greater fish
> carrying capacity - that is governed by the surface area
> of the tank (length X width). Two tanks with the same
> footprint but of differing depths will have exactly the same
> fish carrying capacity. That's physics...

I feel that James is conveying the correct concept with this statement, but
I might've said it just a little differently.

Surface area, turn-over rates and additional sources of aeration combine to
affect gas exchange within the water column and can give the "appearance" of
supporting a larger tank population. But you run the risk of blowing any
kind of safety margin if you stock your tank to a greater capacity than the
_surface area_ alone can support.

Filters and pumps fail, get clogged and slow down, or just simply have to be
removed from the system for maintenance. Then you're faced with a "standing
water" situation for whatever length of time it takes to get things running
again. Planning your stocking levels to the surface area recalls the days
when there was no wide range of devices to circulate the water in an
aquarium and thus increase oxygenation. It is *still* the best way to plan
for emergencies, both foreseeable and not.

The only advantages greater _volume_ gives you is:

its ability to dilute waste build-up to a slightly greater extent, and

a small additional time lag in detrimental changes to the system (reaction


David A. Youngker
nestor10 at mindspring_com