Upside down tank req's extra o2 due to loss of surface area.

by **Peterkarig3210** » Fri Apr 04, 2008 1:29 am

I lost most of the fish in my 10 gallon over 20 gallon USD tank because there was too little surface area and venturi was turned off. I'll have to find a more powerful powerhead so I can have bubbles going up into the USD tank and be simultaneously sucking the air out.

That, or I need to just use the little 3/4 gallon again.

I tried to have the little surface area there was be agitated and it was, but it wasn't enough. This kind of tank set up requires that there be a good enough amount of surface area and the USD tank must be no where near the size of the bottom tank interms of size of opening.

I'm having trouble finding a powerhead that has a powerful enough venturi to pull water up 11-12 inches. You can do this tank w/out a venturi and suck the water up with your mouth, but you better have a big area of open water with good surface agitation or your fish won't get enough oxygen to stay alive.

by **snowboss** » Fri Apr 04, 2008 1:57 pm

DAMN IT !!! PK.............sorry for the lose,

really great learning curve though - would a cylinder or hex tank limit the surface area used in the 20 gallon tank? although that brings you back to the venturi issue eh? a smaller diamiter tank would have a taller "head" to lift..interesting....rest assured we all learned from your lose....Snowboss

by **Peterkarig3210** » Fri Apr 04, 2008 4:38 pm

I still have a few different powerheads to try. I think it probably looks better to have a bit of a surface on the lower tank anyway, as it gives some perspective.

Yea Snowboss, the ability to pull water up into the tank isn't dependant on the diameter of the tank, only the height.

by **snowboss** » Fri Apr 04, 2008 6:21 pm

well.....to a point

i.e a ten gallon tank at 12X18X12 is 216 cubic inches of water per inch of height to lift 12 inches - - a 10 inch cylinder is 78.5 cubic inches per inch of height ......so 216 cu in. divided by 78.5 = 2.75......

so in theory you can lift water in a 10 inch cylinder 2 and 3/4 times farther in height with the same energy used to lift the water in the 10 gallon tank 12 inches ... that would be 33 inches in the cylinder...................

........................asuming the 10 gallon measurements are the same as I used in my math of course

by **Peterkarig3210** » Fri Apr 04, 2008 9:32 pm

I'm not exactly sure I read you correctly. Are you saying that diameter 'does' influence the force, or negative force, required to pull water up to a given height?

Does that mean you can pull a narrower tank easier than a wide tank? I thought it didn't matter. Twas never a math genius to be sure, but if you're a diver and you go under water the size of the body of water you are in doesn't influence how much pressure the water will influence on you. Right? Maybe it's not the same kind of situation? Maybe it has to do with the diameter of the venturi's nozzle, and we would refer to a column of water 12 inches high above that orifice the width of that orifice. Right?

by **Snowboss4492** » Fri Apr 04, 2008 9:57 pm

lol you answered your own question ...if you are under 100 feet of water in a nuclear sub or in a garbage can your exactly right it's the same pressure...........but we are talking about surface area and weight to lift....not depth and pressure.

so to answer your question yes to a point it is easier to lift a narrow tank over a wide one......until you get to lifting an equal amount of water - -which would be dictated by the height of the lift.

as far as the venturi goes........it is only capable of lifting what it's capable of ...i.e 30 lbs of water......now 30 lbs in a 10 gallon tank is only say 12 inches, but 30 gallons in a garden hose is many many feet............

ok here maybe this is a better picture - - -

lets agree that the 10 gallon tank is 216 cubic inches per inch of height .....so now take a square hose 1inch by one inch - - -you would be able to lift the water 216 inches with the same effort as 1 inch in the tank....make sense?? - -i won't go into the problem of shearing at that height - -i'm just stating theory here

by **Peterkarig3210** » Fri Apr 04, 2008 10:10 pm

Are you sure???? I'll try this with the little 3/4 gallon tank, but I'm not convinced. I think you have to think in terms of a column of water the diameter of the venturi nozzle and the height of the USD tank. No?

With what you're saying you would be able to make a continuous flowing siphon with the right combination of tank sizes, with water flowing from one to the other.

You would get some weird things going on. Maybe???

by **Peterkarig3210** » Fri Apr 04, 2008 10:21 pm

If you had a column of water an inch in diameter and 100 inches high, and the bottom was connected to a tube that connected to another column of water 10 by 10 inches and 1 inch deep, and the bottoms of both tanks was at the same level, you would have the water surface levels balancing out. The 1 inch deep 100 cubic inch tank would not push the water in the 1 by 1 inch column up 100 inches. I think it's a similar equation with the USD tank. Right?

On a separate note, trees don't have to deal with the incredible weight of water because they work with capillary action to get water sometimes 100's of feet in the air.

by **spongebob4460** » Fri Apr 04, 2008 11:36 pm

peter try sucking the air out with a hose... then once you have a nice little amount left at the top, you can recycle this air with the venturi... it shouldnt require any new air to be drawn out. Is there a chance your tube filled with water and this caused the venturi not to draw air?

by **Snowboss4492** » Fri Apr 04, 2008 11:53 pm

PK, what you described is basically a water level...long hose with water in it......you fill it until you are at the marked spot you want then where ever you take the other end {as long as it will reach,lol} the water will be at the same level as the other end......BUT...the reason for this is atmospheric pressure ...which we are all subject to....the only thing allowed to break that rule is a vaccum....which is what you are creating with the venturi.........I still stand by my statement that a given equal amount of vaccum will pull the same amount of water up a column with equal results , if 12 square inches rises 1 inch then 1 inch will rise 12.....

Upside down tank req's extra o2 due to loss of surface area.

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