Blog Comments

I'm glad you are willing to give me the benefit of doubt. I have seen misunderstandings like this turn ugly on other forums.

Perhaps I could have better started my original post by saying, "My understanding of how and why skimmers work isn't as complete as I'd like..." My reuse of your wording was accidental, rather than being an attempt at mockery. Honestly, even after you had quoted both posts, I didn't realize I had started and ended my post with the same phraseology you'd used. I can see how that might come across as argumentative. In the future, I will try to choose my words more carefully.

Thanks for being willing to grant the benefit of doubt and once again, I am sorry for any offense.

Now back to the discussion...

I understand your point of view...ie small, non changing bioload with an increase in total system volume should mean the skimmer can stay the same size. After all as I've seen Marc post previously, "the solution to pollution is dilution". However, based on the limited internet searches I'd done when choosing a skimmer for my upgrade from a 29 gallon tank to a 75 gallon tank, it was/is my understanding that skimmer size is proportional to total system volume. Some manufacturers/internet sellers seem to post charts determining skimmer size based on system volume and bioload. Some even suggesting that the same skimmer can be used on say a 100 gallon tank with a small bioload as with a 75 gallon tank with a large bioload.

This line of thinking made me wonder, if someone had a very large system volume, say 1000 gallons, and a very small bioload, say a goby, could a skimmer designed for a goby tank, say 29 gallon or smaller, efficiently remove organics from the 1000 gallons.

The discussion in this thread and the question above is what lead me to do more internet searches to get a better understanding of how and why skimmers work.

After reading several things, including the information at the link I previously provided, I don't believe a skimmer designed for a very small tank could keep up with a very large water volume even with a small bioload. This is all just theory of course because the original question was will the skimmer baker.shawn currently has continue to work after adding a sump (approximately 50 gallons to the system volume).

I could be wrong, and I'm willing to learn differently, but I believe, based on what I've read about contact/dwell time and how system volume and the flow through the skimmer effects dwell time that a larger skimmer would be needed for a larger volume of water. The two important factors to making a skimmer work efficiently appear to be (1) getting every drop of water in the tank to remain in contact with the air bubbles in the skimmer for a maximum amount of time (suggested by researchers as up to two minutes for some organics) and (2) the size of the air bubbles.

Based on the information in the link I posted above (which seems to reference information from Peter Escobal as did Blown76mav's last post) the total system volume needs to pass by the column of air slowly enough to remain in contact with the appropriately sized air bubbles long enough for the organics to be electrically attracted to the air bubbles.

For illustrative purposes let's use my example above. Since we're talking about adding 50 gallons for a sump to a system with a skimmer that isn't sized for the extra 50 gallons, let's also assume the skimmer is a properly adjusted quality skimmer and the air bubbles are the correct size. Based on the formulas derived from Peter Escobal's research, the flow rate through the skimmer should be F=9.2G/T. Escobal stated that T should not be more than 2-3 times per day so for the 29 gallon reef the recommended flow would be 9.2(30/(12 or 8)) = 23 to 35 gph. Using the same formula for the 1000 gallon tank, recommended flow would be 766 to 1150 gph. Using a chart from Escobal's book, the skimmer diameter for the 30 gallon tank would be 2.5" to 3", while the chart doesn't show a 1000 gallon tank, the diameter of the skimmer for 500 gallon tank would be in excess of 9".

As you can see by using Escobal's charts/formula the skimmer sizes and pump sizes for the skimmers are quite different for these two systems. This would seem to imply that to maintain appropriate contact/dwell time, system volume does have a very important impact on skimmer size.

Blake

Originally Posted by blakew

What I assume based on your comment you feel my comments were meant as sarcastic and a personal attack. I can assure you neither is the case. I sincerely apologize that my comments were apparently misconstrued as an attack. I don't post on many forums that I read for fear of just such a case.

The discussion about skimmer sizing was interesting to me and not knowing nearly as much as I would like about the subject (ie as posted above "I'm no expert" ), I decided to do a little research. I found the link I posted above, which suggests, based on someone else's research, that for a skimmer to work at it's peak efficiency the amount of flow through the skimmer (gph) and the contact time have specific relationships with the total system volume. Specifically, while a larger system volume with low bioload may not require as large a skimmer as a larger system volume with a high bioload, a larger total system volume will require a larger skimmer.

I understand that written word on post/email/text messages are read without the benefit of seeing facial expressions or voice/tonal inflection and that they can be misconstrued very easily. Once again I would like to apologize that my post was not worded more carefully to avoid such misconstruction.

I do desire to participate and learn from this and other forums, but have no desire to offend. As such, I will politely bow out of the conversation.

Once again, I most sincerely apologize that my comments were perceived as an attack.

Blake

Blake,

The reason I thought that was because you used the same beginning and ending statement as my initial comment. I don't like to offend either and I'm sorry I misunderstood yours as being sarcastic. I guess I just got overly touchy because I saw my original phraseology and thought you were repeating that as a way of shutting my down. I always appreciate the information contained in these posts. I was merely trying to explain my thoughts on why this was a special case and apparently you were just trying to contribute so my apologies for the misunderstanding and please don't let my misinterpretation stop you from taking part in the discussion. Again, I should have realized that my beginning and ending sentences are fairly common phrases. I'm really sorry.

-Jeremy Pepper

What I assume based on your comment you feel my comments were meant as sarcastic and a personal attack. I can assure you neither is the case. I sincerely apologize that my comments were apparently misconstrued as an attack. I don't post on many forums that I read for fear of just such a case.

The discussion about skimmer sizing was interesting to me and not knowing nearly as much as I would like about the subject (ie as posted above "I'm no expert" ), I decided to do a little research. I found the link I posted above, which suggests, based on someone else's research, that for a skimmer to work at it's peak efficiency the amount of flow through the skimmer (gph) and the contact time have specific relationships with the total system volume. Specifically, while a larger system volume with low bioload may not require as large a skimmer as a larger system volume with a high bioload, a larger total system volume will require a larger skimmer.

I understand that written word on post/email/text messages are read without the benefit of seeing facial expressions or voice/tonal inflection and that they can be misconstrued very easily. Once again I would like to apologize that my post was not worded more carefully to avoid such misconstruction.

I do desire to participate and learn from this and other forums, but have no desire to offend. As such, I will politely bow out of the conversation.

Once again, I most sincerely apologize that my comments were perceived as an attack.

Blake

Well, I'm no expert on skimmer sizing (and with a Vertex IN-180 running on a system that will have less than 100 total gallons you might find this amusing coming from me) but I believe that when you size a protein skimmer all you need to consider is the DT. Theoretically the sump should not be contributing to the bioload. The main load placed on the system is the determining factor. So, for example, a 30 gal. reef tank may have as much bioload as a 75 gal. fish only and would therefore require the same size skimmer. My skimmer claims to be rated for a 180 gal. reef tank so... pretty sure I'm good, but my point is that I could easily get by with a much smaller skimmer and I believe the same goes for you. Having that extra 50 gallon sump won't increase your bioload at all and therefore I don't think it should change your skimmer sizing... Anyway, just my two cents worth.

I'm no expert, but as I understand the principles of how a skimmer works, for maximum efficiency a skimmer should (1) pass the volume of the tank through it no more than 2 times per day & (2) maintain water to air bubble contact (dwell) time as long a possible (some organics require a dwell time of approximately 2 minutes to electrically attach to the air bubbles).

The only way to push more water through a skimmer while maintaining dwell time (all other things being equal) is to increase the size of the skimmer.

The end result would be the same volume of skim mate (because its the same volume of pollution in the water) but to maintain dwell time you have to have a larger skimmer volume for a larger volume of water.

Here's a link that may be useful: http://www.hawkfish.org/snailman/skimmer101.htm

Just my two cents worth,

Blake

I appreciate the sarcasm.... I was enjoying a nice conversation and wasn't trying to be personal, but thanks for taking it to the personal level. Neither the OP or MAV did that.

I'm no expert, but as I understand the principles of how a skimmer works, for maximum efficiency a skimmer should (1) pass the volume of the tank through it no more than 2 times per day & (2) maintain water to air bubble contact (dwell) time as long a possible (some organics require a dwell time of approximately 2 minutes to electrically attach to the air bubbles).

The only way to push more water through a skimmer while maintaining dwell time (all other things being equal) is to increase the size of the skimmer.

The end result would be the same volume of skim mate (because its the same volume of pollution in the water) but to maintain dwell time you have to have a larger skimmer volume for a larger volume of water.

Here's a link that may be useful: http://www.hawkfish.org/snailman/skimmer101.htm

Just my two cents worth,

Blake

Suit yourself, but if you don't change the input/output relationship then you haven't changed anything that would necessitate a bigger skimmer. And while I completely agree that in most systems (where the sump is incredibly small compared to the tank) not processing water would lead to increased contamination, I don't agree that the efficiency of a process would cause it to get behind. Either it's capable of removing the amount of contaminants being released into the system, or it is not. If it's not then it would get behind on both systems. So while the process efficiency is not 100% that would not effect the removal rate in the slightest bit as we are comparing the same machine in systems of differing sizes. Also, the amount of throughput in the skimmer is yet another way to change the rate at which contaminants are being removed. The more you process the more you remove, the more inefficient your system, the more you must process. But as long as you don't hide your skimmer in a far corner of your tank (versus plumbing it into the return line or some similar scheme) then all the water will get processed. The more I have thought about this the more convinced I have become. I've obviously never run such a system, because nobody wants to put their money into a sump that's 10 or 20 times the volume of their display tank. However, this conversation has made me want to experiment with this, because your argument implies that the water volume of a system is as big a contributor to skimmer sizing as the bioload of the display tank. I don't buy that, but I'd like to experiment with it as the results would certainly be informative.

Sorry I still don't buy the "you haven't changed the rate at which contaminates are being added" That isn't the problem, the problem is the skimmer can't remove 100% of the contaminates. If a skimmer is only 20% effective and the tank only system is 100g, (with a skimmer rated at 100g) its only removing 20g worth of contaminates. Leaving 80g dirty. (same skimmer)If we increase the water volume to say 150, It removes 30g and leaves 120 dirty, we are now 20g of dirty water over the rating. Over time the dirty water will continue to rise, hence water changes, but unless your doing 100% even those have a diminished return.

But since neither of us are "experts"

I decided to do some digging and did find an expert on this subject, here's a small part of how to calculate for your skimming needs.


I found a few principals (Aquatic Systems Engineering by Peter Escobal)

Ideal skimming would be 2 - 3 tank volumes a day.
The formula for this is:
(total tank and sump volume / feed rate gph) X 9.2 (this is purity coefficent that will yield 99.9% processed water) = hours till processed

The goal of 2 - 3 times a day means we need to process every 8 - 12 hours.

Peter thinks the sump is important. I guess were gonna have to agree to disagree on this.

Well, you still haven't changed the rate at which contaminants are being added so provided that is the case I still say the current skimmer would work just fine. Provided you don't change the rate at which waste is being put into the tank you will not change what slimmer is needed. That skimmer would take a long time to get to the saturation point, but the saturation point wouldn't be any different than it is in the small tank. Now, when you talk about adding 1000 gallons of water I believe that you would find that everything from dust to flies would change your equation, but provided that you can somehow prevent that additional input you will not have changed the input/output relationship of the waste cycle, so no, I still say that the skimmer has to obey laws of conservation. Yes, the response of the skimmer to contaminants would be "slower" but that's because the added capacity (or capacitance) would damp their effects. All increasing the water capacity should do is slow down the system's steady state time constant.

Originally Posted by pepper'scove

@mav:



Well, I'm gonna butt in again. I understand where you're coming from as well. However what you are insinuating is that a skimmer will allow a bigger tank to get dirtier even though the only thing that changed about the hypothetical system is the water volume. However, your skimmer would still start functioning at the same water contamination level (ppt or ppm of contaminant) as it did previously. Additionally, contaminants would still be being manufactured at the same rate. Thus, as long as you don't increase the rate of waste generation by adding new corals, fish, or other livestock that require additional feeding, and as long as you keep the same skimmer, the contamination of the water will remain constant when taken as a ppm or ppt reading.

So if I add 1000 gallon sump your saying my skimmer I have now will keep up? I think that in the beginning it would but over time given that a skimmer can only skim so much that the body of added water will eventually become saturated with contaminants and then start causing problems. Now with a 1000 gallons added it would take a real long time, but lets say Shawn adds 50 gallons, doesn't change anything else (feedings, fish, or coral) though corals grow thus adding to the waste. I'm sure within a given time frame say a year (I'm no chemist) that water will become just as contaminated as the rest and then the skimmer will no longer be able to be effective for the system.

With contaminates being manufactured at the same rate, the skimmer would have to be 100% effective for this not to happen. I can tell you my skimmer isn't 100% effective and I'm pretty sure there isn't a skimmer out there 100% effective.

@mav:

I can see your point but not sure if I agree. My thinking is even though there isn't any real bio load in a sump the water is still dirty. I know my skimmer doesn't skim 100% of the water that flows past it. And with a given pump size it can only skim so many gallons per hour. So wouldn't the water that wasn't skimmed contribute to the size of the skimmer?

Well, I'm gonna butt in again. I understand where you're coming from as well. However what you are insinuating is that a skimmer will allow a bigger tank to get dirtier even though the only thing that changed about the hypothetical system is the water volume. However, your skimmer would still start functioning at the same water contamination level (ppt or ppm of contaminant) as it did previously. Additionally, contaminants would still be being manufactured at the same rate. Thus, as long as you don't increase the rate of waste generation by adding new corals, fish, or other livestock that require additional feeding, and as long as you keep the same skimmer, the contamination of the water will remain constant when taken as a ppm or ppt reading.

@shawn

From my experience with other systems modeling problems heres a better explanation of why i think what i think. Basically, increasing tank volume while changing nothing else will simply cause the system to start efficiently skimming at some steady-state time constant that is a little bit larger than it would've been before. It's kind of like a capacitive circuit, the larger the capacitor the more energy can be stored in the circuit (think of the capacitance as tank volume and thus the ability to store dissolved organic contaminants) but that doesn't mean that the voltage (contamination within the system) will be any different after a significantly long time period. Rather it just means that the system will take longer to stabilize at the same contamination level. Of course that is provided the current passing through the circuit (think of this as the nutrient import/export transfer rate) remains constant.

I don't know if the analogy to electrical systems helps you any, but such analogies are used all the time to model many different types of physical systems. Anyway, while I think it's great to look for equipment that is future proof, my main point is that the idea that you would have to purchase additional equipment that may make the idea prohibitively expensive, doesn't make any physical sense to me from my experience with systems modeling. Don't know if that helps your decision making process, but I wanted you guys to both have a better idea of where I was coming from.

i know exactly what you mean..i kinda thought about it as i wrote it...but decided to just go with it, however i think having 150gal in the system with a skimmer rated for 80gal is not ideal by anymeans.

mav- you also raise a good point, i remember reading a scienific paper which analyticly compaired a couple types of skimmers, turns out skimmers are only about 20% efficent at removing organics. i think what it really comes down to is pump rates, air volumes, contact time and retention time.

anywho if i do find nutrients are hard to keep under control id probabuly just add another vertex in 80 i really like the preformance and i can always find them cheap.

Pepper,

I can see your point but not sure if I agree. My thinking is even though there isn't any real bio load in a sump the water is still dirty. I know my skimmer doesn't skim 100% of the water that flows past it. And with a given pump size it can only skim so many gallons per hour. So wouldn't the water that wasn't skimmed contribute to the size of the skimmer?

I to run a skimmer rated about 100g more than needed but I know I will be upgrading sooner or later and didn't want to spend the money twice.

Well, I'm no expert on skimmer sizing (and with a Vertex IN-180 running on a system that will have less than 100 total gallons you might find this amusing coming from me) but I believe that when you size a protein skimmer all you need to consider is the DT. Theoretically the sump should not be contributing to the bioload. The main load placed on the system is the determining factor. So, for example, a 30 gal. reef tank may have as much bioload as a 75 gal. fish only and would therefore require the same size skimmer. My skimmer claims to be rated for a 180 gal. reef tank so... pretty sure I'm good, but my point is that I could easily get by with a much smaller skimmer and I believe the same goes for you. Having that extra 50 gallon sump won't increase your bioload at all and therefore I don't think it should change your skimmer sizing... Anyway, just my two cents worth.

Originally Posted by pepper'scove

Glad to hear this was resolved. I was really surprised when I saw this since my own silicone work is (IMHO) superior to what I was looking at. Definitely glad they decided to build you a new one. I still can't believe they sent you this one though... Good luck on the new build!!

yeah when i went to take it out of my dads truck i was less then thrilled, i was even more less thrilled after looking it over, its as if they let the new guy make it!

im not sure what they are going to do with the effed up tank...i hope i can just keep it, i would risk using it as a sump/frag tank just to get that extra 50gal of water volume for stability! but that would mean a bigger skimmer...

blake, that must be quite the job removing all the silicone!!

Glad to hear this was resolved. I was really surprised when I saw this since my own silicone work is (IMHO) superior to what I was looking at. Definitely glad they decided to build you a new one. I still can't believe they sent you this one though... Good luck on the new build!!

i always have my dad reseal all the tanks I get hahahaha

all is good now! they just called, they are going to be building me a new tank this week and dropping it off next weekend!! im very pleased with north american fish breeders customer service! http://northamericanfishbreeder.com/

i should add that what worrys me most is the airbubbles in the seals also the one corner where the silicone is very thin! as for the trim it was just a very shitty job, other than a huge amount of salt creep collecting there and it looking ugly im okay with it....but im very not okay with it lol. ive waited to post on the local forum..i want to wait and see what kind of response i get back from them before i start bashing, this being said there is no way in hell my dad is driving back to get a new tank or drop this one off (he thinks our hobby is a joke...very un-cool) so i hope they get creative

i think its offical, hes either dead or very lost in my tank....after 3 days hes still nowhere to be seen