Michaelshewitt's systems

gemmell

Stuart Chignell wrote:

Aireation is a function of the surface area of water exposed to air over time. There fore the longer a bubble of air is under water the greater the aireation. Smaller bubbles mean greater surface area and therefore more O2. Trade off is that the deeper the air input the less air and the smaller the bubbles the less air.

Horizontal Rotational velocities in tanks create radial currents where water flows along the bottom of the tank to the center up a center coloum of water and then along the top of the water from the centre to the outside. This creates good mixing on sides, bottom and top but not the whole tank. This can be compounded by center drains creating vortex which the fish avoid.

Australian RAS people dont seem to care but in europe and the us they avoid this with water inlets that look like upside down L's. The trunk of the L has to series of small holes that direct water in series of jets along the side of the tank. The arm of the L points towards the center of the tanks with the holes along its length creating jets that promote more even mixing by reducing the irrotaional created by having the water enter the tank from only one inlet.

Coupled with a side top drain this means that a greater % of the tank is inhabited by the fish effectively decreasing density.

That's interesting. My current method of supplementary aeration is to have a "fountain pump" style arrangement going which pulls water up from the bottom and sprays it back over the tank. Not much movement of the water, but I think it aerates pretty well.

The other method is to knock the pump over on it's side and let it create a swirl in the tank. The trout love it, sit right next to the outlet (it's a Ebarra 7000lph pump).

You're saying the swirling water can actually create "dead spots"?

michaelshewitt

Stuart Chignell wrote:

michaelshewitt wrote:

Stuart Chignell wrote:

Aireation is a function of the surface area of water exposed to air over time. There fore the longer a bubble of air is under water the greater the aireation. Smaller bubbles mean greater surface area and therefore more O2. Trade off is that the deeper the air input the less air and the smaller the bubbles the less air.

Horizontal Rotational velocities in tanks create radial currents where water flows along the bottom of the tank to the center up a center coloum of water and then along the top of the water from the centre to the outside. This creates good mixing on sides, bottom and top but not the whole tank. This can be compounded by center drains creating vortex which the fish avoid.

Australian RAS people dont seem to care but in europe and the us they avoid this with water inlets that look like upside down L's. The trunk of the L has to series of small holes that direct water in series of jets along the side of the tank. The arm of the L points towards the center of the tanks with the holes along its length creating jets that promote more even mixing by reducing the irrotaional created by having the water enter the tank from only one inlet.

Coupled with a side top drain this means that a greater % of the tank is inhabited by the fish effectively decreasing density.

Eek! Science! Don't you know, man, we're heading back to a time of rank superstition? Don't confuse me with facts! I want prejudice!
/rant off

I'm trying to make up my mind. It appears I have two options:

Get the water in deep and create rotation
Get the water in shallow and create aeration

Since I can add aeration with a separate air pump - which I will probably need anyway - I'm leaning towards option 1.

I wish I had a picture for this.

For the upside down L inlet all the water entering the tank through the arm of the L is going in on the surface. If the L where up the right way (for an L) then the water entering the from the arm of the L would enter at the bottom of the tank at a right angle to the radius of the tank. This would stuff up the radial current that is ment to move the solids along the bottom.of the tank to the center drain.

Stuart -
Yes, I can visualise this.

I imagine the vertical section is longer than the horizontal in order to attempt to equalise the flow from the two arms, the vertical having the disadvantage of increasing water pressure as it extends deeper and deeper into the tank.

I might get myself a anti-return valve, plumb it into the feed line before the fishtank and give it a go.

I was going to use a foot valve, but they have to be underwater - does anyone know what to use and where to get an inline anti-return valve?

Simo

gemmell wrote:

That's interesting. My current method of supplementary aeration is to have a "fountain pump" style arrangement going which pulls water up from the bottom and sprays it back over the tank. Not much movement of the water, but I think it aerates pretty well.

The other method is to knock the pump over on it's side and let it create a swirl in the tank. The trout love it, sit right next to the outlet (it's a Ebarra 7000lph pump).

You're saying the swirling water can actually create "dead spots"?

I've been told that the majority of airation produced by the air bubbles from an airstone is in the fact that they drag oxygen depleted water from the bottom of the tank up to the top and it is replaced by oxyegen rich water from the surface. Apparently very little oxygen actually dissolves from the bubbles into the water and it is all about water circulation, therefore you want the airbubbles to start form the very bottom of the tank, and Gemmel's fountain is perfect.

I'm not sure how the spray bar method fits in with this theory? :think:

ivansng

Simo wrote:

Apparently very little oxygen actually dissolves from the bubbles into the water and it is all about water circulation, therefore you want the airbubbles to start form the very bottom of the tank, and Gemmel's fountain is perfect.

I'm not sure how the spray bar method fits in with this theory? :think:

Yes, that's what I have read as elsewhere as well. Oxygenation of the water happens when the bubbles break the water surface, not in the water.

I guess the spray bar does agitate/break the water surface. Similar to Gemmell's fountain idea.

michaelshewitt

Not much on the system today, but got a bit done on the shed.

Like so much around here, whoever did the original work was a bit... how's yer father.

Where the pad was carved out of the slope, some genius decided plywood would be the best retaining wall; I am digging it out and replacing it with concrete cylinders (testing cores?) we have lying around:

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On another note, I found several of these floating on top of the fishtank - are they black soldier flies? Please tell me they're black soldier flies...

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Prawnz

Reckon you might have a Wasp there . :think:

daddykirbs

The legs of a BSF are white.

michaelshewitt

daddykirbs wrote:

The legs of a BSF are white.

Prawnz wrote:

Reckon you might have a Wasp there . :think:

Bother.

gemmell

daddykirbs wrote:

The legs of a BSF are white.

Always?

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I've always thought that guy was a BSF, but it has only white segments on it's hind legs... rather than fully white legs. Lots of the other images in google images have the white at the bottom of their legs.

michaelshewitt

Planted plants today!

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Also built an inline anti-return valve, which has made me feel so very clever, I have made a thread for it of its own...

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daddykirbs

gemmell wrote:

daddykirbs wrote:

The legs of a BSF are white.

Always?

...

Ok, I don't know... perhaps not always. I'm not an expert. ALL mine here in Texas have white lower legs.

I'm not sure why my statement was a "bother".

Burnsy

daddykirbs wrote:

I'm not sure why my statement was a "bother".

Think you have misunderstood. I took it that he thought it being a wasp was a bother because he was hoping for BSF

michaelshewitt - great system, love the shed, what an ideal use for it, wish I had something like that lying around on my block.

daddykirbs

ahh, I see. Forgive me.

michaelshewitt

daddykirbs wrote:

gemmell wrote:

daddykirbs wrote:

The legs of a BSF are white.

Always?

...

Ok, I don't know... perhaps not always. I'm not an expert. ALL mine here in Texas have white lower legs.

I'm not sure why my statement was a "bother".

Indeed, as explained below. I was hoping for BSF - free fish food. I don't appear to have them; bother.

michaelshewitt

Burnsy wrote:

daddykirbs wrote:

I'm not sure why my statement was a "bother".

Think you have misunderstood. I took it that he thought it being a wasp was a bother because he was hoping for BSF

michaelshewitt - great system, love the shed, what an ideal use for it, wish I had something like that lying around on my block.

Burnsy -
Yes, it's great to be doing something with the shed - it was just deteriorating, which was a waste.

Thanks for the comments.

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Michaelshewitt's systems

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A place to discuss aquaponics