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Thread: Bigger screen or More watts??

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    reefdiy's Avatar
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    Bigger screen or More watts??

    So here is the deal....I have spent the last couple hours reading all I can about scrubbers. I have researched them before, as well, and I love the idea and the approach to reefing that it offers. All systems go!

    BUT.....I do have one question.

    First let me outline what I am thinking and what my scrubber restrictions are:

    1) 26 gallon bowfront display, no refugium (I hated my last one I had.....chaeto sucks!), a medium CUC, an Anemone, and two clowns.
    I feed about a 1/4 -1/3 cube or equivalent dry food per day (keeping it low till scrubber is up and running as algae and cyano is problem). Don't worry the fish are happy, healthy and growing atm, but I do wanna fatten the little suckers up!
    I plan to increase my bio-load with a couple more fish (2 small fish max), cleaner shrimp and a bigger CUC in the near future. I expect to be feeding at least a 1/2 to a whole cube/equivalent per day depending on what animals I get.

    2) Unfortunately am confined to the single sided design, its just a fact due to sump space, stand, layout ect. (lots could be explain about this). Just know that I have thought it through and I mean thoroughly.....I tend to over-think things.

    3) I have settled on a overflow feed design as I don't feel like/have the money for another pump (I also don't really have the space). My actual measured return flow to the scrubber will be approximately 190-210 GPH (depending on how good my stopwatch finger was).
    According to some simple math that puts me in a range of 5.4" - 6" or so of slot length at 1/8" slot width. I have decided to go with 5.5" of slot as this gives me a good range of about 34.5GPH/PI - 38.2GPH/PI, at the high end (depending on return rate). I am predicting I will get a mean flow rate closets to 35GPH/PI with 5.5" as the average flow was about 200GPH. Getting the flow right is the most important thing to me, as from my experience it is the key to all nutrient export in any filtration system. Have to process the water in order to clean it!

    4) I will most defiantly be running a 9 hour cycle (double the watts) as I am convinced it is absolutely the way to go. This is my second priority because: light=growth.

    I guess that leaves screen size as the third and least important priority (correct me if I am wrong).

    So that being said, the way I see it my options are as follows (based on the new sizing guidelines and the fact that I plan to feed 1 cube per day eventually):

    1) 5.5" by approx. 2.2" (Area 12") screen size with 24watts/9hrs (1/2 cube feeding) - I think this would not be the best option for me. It seems like a screen with those dimensions would simply not perform as well as a more square shaped screen. I also predict that I would be wasting a lot of light as it passes around the narrow height of the screen. This option would also need to be adjusted to 48watts/9hrs for full cube feeding in the future (easy mod).

    2) 5.5" by approx. 4.5" (Area 24") doubling the screen size but staying with 24watts/9hrs (full cube feeding?) - I like this option better as I prefer the screen dimensions and if what I am assuming here is correct I am getting away with less power consumption for the same amount of filtering as a 12" at 48watts. Area is doubled instead of the watts. I have heard on this forum many time "more watts is better" but no one ever says: "more watts is better than more area"

    3) I guess option three is: 5.5" by 4.5" (24" area) screen with 48watts/9hrs (full cube feeding? Seems more like 2 cubes, which is overkill for me) - This might be better math than option 2 as it scales watt to watt with option one, where option 1 is 2watts per sq.in. (9hrs), so is this option. Although it also seems as I already stated like it would have twice the filtering capability of option 1 since the area is doubled and scales with the increased wattage.

    4) Finally, I could do this: 5.5" by 3-4" (16.5-22" area) with 24watts/9hrs and just feed 1/2 cube even though this screen could handle more (I think?) or feed a full cube and increase the light to 10-12hrs.

    feels like I might be going in a circle here......

    So you can see that 5.5" is the limiting factor here, and as I have chosen an overflow feed this slot size can not be deviated from in order to have proper flow.

    So it is defiantly time for a question(s): Do watts and screen size(area) scale proportionally? Or does a bigger screen & less watts not equal a smaller screen & more watts?

    Equation form (for the right brained among us): <Screen + >Watts = X >Screen + <Watts = X where,X=filtering capability, and X=X.

    All advice, theories, ideas and hypothesis welcome!

    PS: I would also like to know if I could maybe make a compromise with 5.5" by 3.5" (approx. area 20") and 36watts (23watt & 13watt bulb for a total of 1.8 watts per sq.in.) /9hrs. This still seems like it is more than 1 cube per day thought. Now that I think of it this option seems like a middle ground between 1 & 2 as it adjusts both area and wattage to a "happy medium" while still maintaining the ratio. I could also play with the leeway I have in the on time of the scrubber. Maybe 20" at 36watts for 10-12 hours could do the trick. Anyways I have rambled on for long enough.....

    Let me know what you think (be creative)!

    Thanks
    -Ben

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    reefdiy's Avatar
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    Pictures will eventually follow...

    -Ben

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    And I am right in understanding that the double screen method (two screens back to back) is now an obsolete practice?

    -Ben

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    5.5" by approx. 2.2" (Area 12") screen size with 24watts/9hrs (1/2 cube feeding) - I think this would not be the best option for me. It seems like a screen with those dimensions would simply not perform as well as a more square shaped screen. I also predict that I would be wasting a lot of light as it passes around the narrow height of the screen.
    Well you have the sizes correct. And it is true that all the light needs to hit the screen for it to apply. So just size it to catch all the light, and use CFL spotlights, which focus the light.

    5.5" by approx. 4.5" (Area 24") doubling the screen size but staying with 24watts/9hrs (full cube feeding?)
    Same wattage on same 1-sided screen = same feeding of 1/2 cube.

    I am getting away with less power consumption for the same amount of filtering
    No, never. Same watts = same feeding. Unless you go 2-sided, which is double the feeding for the same watts.

    5.5" by 4.5" (24" area) screen with 48watts/9hrs (full cube feeding? Seems more like 2 cubes, which is overkill for me)
    One cube.

    Do watts and screen size(area) scale proportionally? Or does a bigger screen & less watts not equal a smaller screen & more watts?
    Double watts = double feeding
    Double area = no more feeding

    As long as the screen is catching ALL the light, then increasing area will only reduce filtering because it spreads the growth out too thin and it does not get a chance to grow out and into the light and flow.

    And I am right in understanding that the double screen method (two screens back to back) is now an obsolete practice?
    Correct.

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    reefdiy's Avatar
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    Quote Originally Posted by SantaMonica View Post
    Well you have the sizes correct. And it is true that all the light needs to hit the screen for it to apply. So just size it to catch all the light, and use CFL spotlights, which focus the light.
    Never thought I would see you recommend CFL spotlights....but I guess for my situation they would work pretty good as my screen area is really small. On the other hand I do have a bunch of black acrylic lying around and some nice reflective insert material......might just DIY me a ballin reflector.

    Quote Originally Posted by SantaMonica View Post
    Same watts = same feeding. Unless you go 2-sided, which is double the feeding for the same watts.
    Double watts = double feeding
    Double area = no more feeding
    This makes perfect sense....I kinda thought you were going to say that.

    Quote Originally Posted by SantaMonica View Post
    As long as the screen is catching ALL the light, then increasing area will only reduce filtering because it spreads the growth out too thin and it does not get a chance to grow out and into the light and flow.
    Sounds good, I really wanna do this thing right and get some excellent green 3D growth.....I think I know what I have to do! Thanks!

    -Ben

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    This may help - go to post #26 just updated the basics

    http://algaescrubber.net/forums/show...cs-The-Summary

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    When considering light "concentration" you have to consider more than screen size, there are a couple other important factors to consider, some of which are often overlooked. Some may disagree with me, but this is my opinion. I am not going to get into specifics, you like to think, and these are some things to think about when designing your screen:

    1: You need enough light, in about the right spectrum, to grow algae on your screen and grow it well. These are the guidelines that are most often covered by rules of thumb, but they can vary somewhat.

    2: Your algae screen has to out compete your tank/sump lighting. If you have incredibly bright tank lighting, you are going to need more "concentrated" light to have a more competitive screen filter.

    3: You need enough light penetration to keep the base algae alive for the period of time you go between cleanings. This is where double sided light really makes a difference, same light = double penetration if split between both sides of the screen. However either with single sided or double sided you can do some things to reduce base algae death, these all have downsides, so some mix of them is probably the best answer:

    a: More frequent cleanings - the less buildup of algae, the less the light has to penetrate, however the downside is if there is not enough algae base to grow well filtration will suffer. So more frequent cleanings, but perhaps dont be too agressive when you clean.

    b: A larger screen (as long as you have enough light meet the first 2 considerations) will allow more surface area for growth and less depth, this will allow more light through.

    c: Bright enough light to penetrate all the way through the algae. The problem with this, especially in a single sided application is that you will burn the surface algae by the time you get light all the way through. However more flow could help this.

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    Too much area, however, and the algae does not have enough nutrients to get thick enough to grow 3D, which is where the most filtering occurs. For most people, 3D will start at about 5 to 10 days, and if you clean too soon you will never get it.

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    Quote Originally Posted by SantaMonica View Post
    Too much area, however, and the algae does not have enough nutrients to get thick enough to grow 3D, which is where the most filtering occurs. For most people, 3D will start at about 5 to 10 days, and if you clean too soon you will never get it.
    I will take your word that 3D growth is optimal, and once you get an automated feeding system to feed the crap out of your tank on a semi continous basis you might need something like that. However, personally I can tell you that I feed about 2 cubes a day and that my dual 13x10.5" (or whatever the standard size sheet is) are only lit from one side by 26 watt CFL bulbs and after a month of running, even the high spots of algae are barely at 1/4" of growth, yet my nitrates and phosphates are always below measurable levels.

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    Correct, because you are not feeding that much. The screen could be much smaller, however, and do the same filtering, if it would be allowed to grow thick green.

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