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Old 10-16-2006, 03:09 PM   2 links from elsewhere to this Post. Click to view. #1 (permalink)
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Wet vs. Dry Skimming

Ok this has been brought up many time well I’m going to put it to the test.

I’m currently setting up an experiment to test the effectiveness of each technique. I will be setting up 2 10gal tanks each with a whisper 10 with no media in it. Both tanks will have a Current USA Fission Nano Skimmer on it. I will allow the tanks to run for 7 days without the skimmers attached before starting the test. I will drill a hole in the bottom of the collection cup to drain the skimmings in a container. Both tanks will be placed under a standard 48” shop light with standard florescent bulbs. I will then add 1 cube of San Francisco Frozen Brine Shrimp Cube 3.5oz every other day for 14 days. On the 28th day I will take the skimmings and dehydrate them. Weigh both skimmings and record the findings. i will repeat this test 3 times to verify the data.

I am open to suggestions on ways to improve this test so please feel free to contribute. If anyone has 2 identical skimmers that they are willing to part with I will use them instead to help reduce costs.
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Old 10-16-2006, 03:38 PM   #2 (permalink)
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Great idea! I will be excited to hear about your findings.

Many say dry skimming is more efficient, but I don't think efficient is necessarily the best word to describe it. Certainly there will be more particles in a cup of dry skimmate than a cup of wet skimmate, but could the wet skimmate actually be removing more particles even though you may have to empty the cup more and add water to the system more often?
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Old 10-16-2006, 05:47 PM   #3 (permalink)
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when i saw the heading i thought to myself, "oh hear we go, this topic is ripe with preference". i was surprissed to see an experinment in the winds, good work. will follow your progress
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Old 10-16-2006, 07:28 PM   #4 (permalink)
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Great experiment. I think that it is great that we are really looking at things in a scientific manner.
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Old 10-17-2006, 01:30 AM   #5 (permalink)
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I have a fission nano skimmer. I never ever found a way to get it to skim dry. It always overflows the cup. Something to do with the filter ring plugging up. I finally gave up on the skimmer much like everyone else that bought one. Between looking at micro bubbles and it emptying a half gallon of tank water in 8 hours it just wasn't worth it. Let me tell you I tried to get this skimmer to work and I just couldn't.

Oh and just so you know the skimmer cup should have a drain already, fits standard air line tubing.
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Old 10-17-2006, 02:39 AM   #6 (permalink)
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I have a fission nano in our 29g and if it gets cleaned every week it skims "fairly" dark, but still wet. The real problem is wet skimming wastes more water and the fission's performance is seriously impacted if the water level changes.

Clean filter pads ("pristine", actually) are the key to stopping microbubbles with the fission. You can soak the old filter pads in bleach to make them last a little longer, just make sure you rinse them really well with a dechlorinator. Don't rub or squeeze them when you clean them, though, because if they tear or pull apart they'll be useless and you'll see microbubbles again.

I keep a clothes pin clamped onto the airline tube we've got attached to the drain and unclip it once or twice a day to drain the cup. I've got the other end running into an old 2 liter soda bottle which will almost fill itself once a week -- for the amount of stuff this skimmer pulls out with 2 liters of water a more efficient skimmer would probably only pull a cup or so of water -- it does pull it out, just not as efficiently.
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Old 10-17-2006, 02:48 AM   #7 (permalink)
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Quote:
Originally Posted by PreauxPhoto View Post
I’m currently setting up an experiment to test the effectiveness of each technique. I will be setting up 2 10gal tanks each with a whisper 10 with no media in it. Both tanks will have a Current USA Fission Nano Skimmer on it.
The Fission is so sensitive to water level that I don't think you'll get any sort of accurate test results without an auto-topoff system on each tank. A water level change of 1/4" or so can mean the difference between a quart of wet skimmate or an empty collection cup -- or worse, if you've got an airline tube on the drain running to a small bucket or bottle it could mean a gallon of tea-colored water all over the floor when the bucket overflows.
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Old 10-17-2006, 03:12 AM   #8 (permalink)
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FANTASTIC, the tools for the job are at hand!
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Old 10-17-2006, 05:54 AM   #9 (permalink)
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Ah yes, discussion, debate, test, measure results, report, discuss, debate, come to conclusion once and for all. Sounds great! However, I see a problem before it begins and this is part of the discussion at the beginning, right? Let's call what it is we want to remove by either method of skimming "matter" for lack of a better word. We could simply call it "skimmate" except the resulting difference between wet and dry skimmate will be excess water and that's not what we want to measure. We are trying to remove "matter" and for this discussion we are trying to measure which method, wet or dry skimming, will remove the most "matter" not total volume of "skimmate", correct?

Let's assume all other factors are equal, and they should be, except the difference between the wet and dry skimmate. The wet skimmate will, by it's very nature, have more water volume to it. That water will have less of the substance "matter" we are hoping to pull out of our system because by volume you have the "matter" we are looking for plus excess water. It isn't necessary to pull out excess water. That fact actually is the answer to your test. In order to remove x amount of matter wet, you have to remove x plus the amount of extra water you have in the mix. Why would anyone want to remove extra water. It simply dilutes x, takes up volume in the collection cup and makes you add water to replace what you are removing. Doesn't make any sense to skim wet to me. That brings up another flaw to overcome.

When you dehydrate the two skimmate solutions, the wet skimmate will have more substance volume because it will leave behind salt from the skimmate solution, not just the "matter" we are looking to remove. So, in my humble opinion the test isn't going to result in an accurate answer and the debate will continue long into the future. I do have a suggestive solution to the debate. Whether you want to hear it or not, you know I'm going to give it to you.

Let the advocates of either method use the method of their choice. Hmmm, no need for a test doing it that way. Besides I've had skimmers that by design or flaw have produced wet or dry skimmate and I'll take the dry, thick, scummy, smelly, rotten junk as being the most important "MATTER" to remove from my system and do regular water changes for replenishing my water.

I'll be the first to admit, I'm not a scientist and my method may be crude but I'll put my dry skimmate up against any wet skimmate any day. And, that's my word. What's your's?
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Old 10-17-2006, 08:55 AM   #10 (permalink)
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This is EXACTLY why i posted here before i started the test!!!!

This place is such a vast well of knowledge ok the nano's out, i'd like some suggestions for cheap replacements. less than $50 per. Please

well everyone brings up a lot of good points. i hadn't thought about the salt in the wet's collection or the ato. I have an ATO i can spare to do this.

i dont think i'm willing to just drop it though i have a skimmer that has the ability to do both and i want to know which is better for my own piece of mind.

i just need to figure out how to strip the salt......... any ideas?

i will be bringing out the big guns for this though. I work in a R&D laboratory at Marshal Space Flight Center for N.A.S.A. and i have been given approval to use one of our labs to do this test "though on my own time of course" and any of the equipment i need. i will be talking to some of our chemists and engineers to get their opinions on how to concure these hurdles.

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Old 10-17-2006, 10:38 AM   #11 (permalink)
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Ok let me pass this by the group and get some feedback.

What I’m thinking to do it get around the salt problem is to add more.

I will also set up 2 controls one will be a fresh mix of saltwater and a tank that has ran for the same amount of time but with no food added.

Lets say if at the end of the test I have 1000ml of wet skimmate and 250ml of dry skimmate what I will do is dilute the dry skimmate to 1000ml till they both have the same volume and SG there for the only variable will be the dissolved organics. Then I will use either a refractive index or a spectrophotometer to measure the amount of light absorbed by both solutions at a known volume (I.e. 5ml). From this I will be able to tell which one has a higher concentration by the amount of light absorbed.

Once I have this data I can dehydrate both samples and weigh them with the salt content being equal between all samples and controls I can then subtract the controls weight form the samples weight to get a rough volume of dissolved organics. Since I know the SG of all the samples I can calculate the PPM/volume and from that I can get the total amount of salt in the samples, therefore hopefully removing the problem of salt content in the sample.

Because I believe the dehydration method is not as precise I will only be using it to back up the refraction test and hopefully get the same greater than or less than result.
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Old 10-17-2006, 11:26 AM   #12 (permalink)
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Quote:
Originally Posted by PreauxPhoto View Post
Lets say if at the end of the test I have 1000ml of wet skimmate and 250ml of dry skimmate what I will do is dilute the dry skimmate to 1000ml till they both have the same volume and SG there for the only variable will be the dissolved organics.
Just a note: Wet skimmate typically has a lot of un-dissolved organics like uneaten food, live pods & worms, even cat & dog hair (ok, maybe you won't have cats and dogs in your lab, but my living room doesn't have NASA-grade security!).
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Old 10-17-2006, 11:50 AM   #13 (permalink)
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wow doc it sound like you have a shedding problem " malcom and andy are beautiful though" i miss my cats :-(

but any way do you feel that the food and pods would shift the results? or since it's a controled BB tank should it even be a factor?
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Old 10-17-2006, 12:02 PM   #14 (permalink)
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I think it could shift the results since even if both samples end up being equal the sample from the dry skimmate would have more protiens and surfactants because of how wet & dry skimming tend to pull different things out of the water. I remember hearing Anthony Calfo and other industry gurus mention on more than one occasion that running 2