
03/14/2018, 11:57 PM  #976 
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You're missing the fact that if they are both 2 cube/day screens, then they have the same LxW area.
Tank #1 screen with a 6" wide screen would have to be 4" tall = 24 sq in Tank #2 screen with a 12" wide screen would have to be 2" tall = 24 sq in Tank #1's screen would receive 1/2 the total flow, but each pass makes contact with 4" of vertical algae growth substrate. Tank #2's screen gets 2x the [total] flow of #1 but each pass makes contact with only 2" of vertical algae growth substrate. All other things being equal, those 2 scenarios are nearly identical. [edited]
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03/15/2018, 12:28 AM  #977  
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Look at this way. A fraction of the aquarium' inorganics are filtered from it's water each time its volume passes through the scrubber. So if you have a tank turnover twice an hour through the scrubber it will remove twice the fraction of inorganics that is does with only one tank turnover through the scrubber per hour. Now on tank #1 if we double the turnover, we will have to do it by doubling the speed of flow over the screen, and I think we agree that doing this will not increase the fraction of inorganics removed from the water. You can double or tripple the flow through the scrubber, and as a consuquence, double or tripple the TTR, but if increasing the speed of flow through the scrubber doesn't increase the fraction of inorganics taken out of the water, it will make no difference. But if we double the width of the screen without doubling the surface area, and we double the flow over the screen without increasing the speed of flow we do increase the fraction of inorganics removed. 

03/15/2018, 03:51 AM  #978  
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Widening the screen without increasing its surface area doesn't increase the filtering, it just means you need a bigger pump. LOL what if you doubled the flow over Tank #1 screen, would this increased nutrient uptake over a 24 hour period? What got me think about this TTR thing is that a scrubber removes a fraction of the available nutrients with each tank turnover through the scrubber. So you need multiple tank turnovers every 24 hours to remove 100% of the nutrients or you get rising nutrients. We don't know the value of the fraction removed, so you cannot calculate the number of tank turnovers needed. How was the cube equivalent  screen size calculated without knowing these imputs? was it a guess that just worked ??? 

03/15/2018, 09:25 AM  #979 
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The cube equivalent was developed by Bryan / Santa Monica, basically from what I understand he took 2 of his SM100 scrubbers and put them on a 90g tank and then fed liquid coral food according to his developed cubeequivalent measurement method, and then basically fed the equivalent of about 22 cubes/day for a length of time, then figured that this feeding rate was about the maximum that those 2 scrubbers could handle.
Then he did total screen LxW area divided by cubes/day and came up with 12 sq in per cube of food per day. IMO that one has stood pretty solid as a rule of thumb. There are ways to make a certain size screen more efficient by designing to encourage 3D growth
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03/15/2018, 03:33 PM  #980  
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What are these ways & what is 3D growth exactly 

03/15/2018, 07:09 PM  #981  
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S.M. had to work it out using a practicle method because the fraction of inorganics removed is unknown, so the TTR cannot be calculated. Practicle testing is best of course because its used to test a theoretical conclusion. I see now how considering both TTR, and the cube  screen size method, at the same time as though their two seperate issues is wrong, because the TTR is built into the cube  screen size method already. 

03/16/2018, 09:35 AM  #982 
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3D growth is what you get when you enclose the scrubber in a box that is small enough such that the growth touches the walls and traps water like this:
I believe it was SM that first noticed this effect in his SM 100 scrubber, the box would fill up with algae growth and once this started to happen, the growth seemed to take off somewhat exponentially for a period of time. I've had some harvests where the growth was so densely packed, it came off like a slab.
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