Water Height / Depth, Ideal Tank height, best depth Options

[YLD]

Hi,

Anyone got any idea what the idea tank depth/ height for both top view and side view ranchu?

[awrieger]

Apologies for starting a new thread, Desireless. I did a search for 'depth' and this thread didn't come up.

I've done some quick research and calculations about water pressure in different sized tanks;

Pounds per square inch = Weight in lbs / Area in square inches
(a cubic foot of water weighs 62.5 pounds)
NB. For purposes of discusion, dimensions are length x height x width

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So, for a 4' x 2' x 2' tank:
volume in cubic feet of 4' x 2' x 2' = 16 cubic feet
16 x 62.5 pounds per cubic foot = 1000 pounds

area of the bottom of the tank in square inches, 48" x 24" = 1152 sq inches
Pressure at the bottom, 2' down = 1000 / 1152 = 0.86psi
Pressure exactly mid-tank, 1' down = 0.43psi
Pressure 6 inches from surface = 0.215psi

The pressure is literally 50% at 50% of the height, and so on. So a tank the same length and width but half the height has half the pressure, etc.

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The same length and height but 50% width at 4' x 2' x 1' = 0.86psi.
100% the 4x2x2 pressure.

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The same height, but 50% both length and width at 2' x 2' x 1' = 0.86psi.
100% the 4x2x2 pressure.

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The same length, but 50% both height and width at 4' x 1' x 1' = 0.43psi.
50% the 4x2x2 pressure.

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50% of all three dimensions at 2' x 1' x 1' = 0.43psi.
50% the 4x2x2 pressure.

CONCLUSION:

Roughly, the only thing that makes a difference in water pressure is height. Length and width make no difference. So a 2' high 120 litre tank has the same water pressure as 2' deep 120,000 litre pond.

6" deep is 0.215 psi
1' deep is 0.43 psi
2' deep is 0.86 psi
3' deep is 1.30 psi
4' deep is 1.74 psi

So the approximate simple rule is the pressure is a multiple of the height/depth. eg, 2 foot deep is double the pressure of 1 foot deep, 3 foot is double the pressure of 1.5 foot, etc, etc.

So moving a fish from 18" to 24" as I plan to do is a 33% increase in pressure. So I tend to agree with you both that small enough change should be okay, so I'm going to do it.

But the question remains - what is the maximum ideal pressure for goldfish? 0.75 psi? 1.0 psi? A fish may cope with it, but is it healthy and ideal?

A fish can adjust it's buoyancy via its swim bladder to equal the water pressure, but at what point does the pressure overwork the swimbladder and is unhealthy for the fish? Especially if swimming from the top to feeding at the bottom of the tank where the pressure is greatest? Is it dependent on the fish's size? A shallow fry raising tank compared to an adult's deeper tank? Or even the breed of goldfish requires different? I see Tiku breeders in Malaysia keep the water at only 10" deep in their ponds, whereas it's mentioned before in this thread Chinese farmers have 3' deep ponds.

[gohks]

It's generally true that depth of water play a part in swimmig well being of Ryukin. I have Ryukin that overturn in deep water but recovered when change to shallow one.
Not sure you will get an answer if you go too scientific. I follow the general rule of thumb since size of fish also play a part. I use the max 1:4 ratio rule, that's taking into consideration the height of fish minus the fins, the max water height you can have is 4x. )