Gravity versus Feed Pump Skimmer Debate

[aquavista99]

This thread was split from the original thread of Tim's 300g tank to preserve the original thread and to keep a good debate alive.

[bigfalcon36]

I'll be sure to post the reply to my email from Deltec.  Hopefully, I get the skimmer tomorrow...it shipped out on Tuesday.

I think we keep the debate going.

Bottom line though...your skimmer, your water, your tank, your decision.

[JSLeedy]

Bottom line though...your skimmer, your water, your tank, your decision.

Agreed.  You right to choose.

Sorry had to say it after that last statement.

[Baggerhog]

I am not trying to argue but merely trying to provide more input. The statement regarding constant pressure is the same statement that has been stated by other builders. To ensure you get constant pressure you can reduce the pipe from 1.5 to 1" this will increase the pressure going into the skimmer. There needs to be a gate valve or a good quality ball valve to adjust your flow into your skimmer. There needs to be a T fitting between your valve for the skimmer and the tank. The T will allow the drain water to exit what is not taken into your skimmer. The exit of the T will then go to your sump. To be the most scientific a test of using a skimmer on a system that was first feed with a feed pump and then switched to direct feed will answer this question. Maybe Joel will chime in since we were talking about this very topic when I noticed his euro reef RC500 was a direct feed from his tank. He said he is getting better results since switching from pump fed to direct feed. Anyone who has a sump that is glass or acrylic can see the build up of desitrus where the drains enter even if you are using filter bags. I can verify this as my old setup with a 180 gallon sump would reflect the build up. I had to vacumme that chamber. Joel, please share your wisdom if you dont mind entering the debate. This is more for the people who have skimmers that are not oversized for their tanks. I am just sharing to help those folks out. Some skimmers cannot be direct fed because they are not recirced.

[bigfalcon36]

Andy, nice info.  I dont want to be a pain, but is there a way to prove a generic drawing of the 'T' you're talking about.  i want to get this right the first time around. 

For those interested in what Deltec has to say, here is their reply to my email:

Feed Supply...The skimmer should be provided with water from the aquarium system either under pressure from a separate feed pump or by gravity supply.

For a pumped system use our installation kits or choose a suitable pump and pipe diameter using mentined in the user manual and connect it to the inlet of the unit. Rigid or flexible pipework can be used for this task. Connect up the outlet pipe to allow water to return to the system.

It is recommended on smaller skimmers that a ball valve is fitted on the outlet pipe to achieve better adjustment of the water level. Larger models may come supplied with a coupling at one side of the ball valve to allow the riser tube to rotate for easier installation.  If gravity feeding the skimmer, it is necessary to fit a tee piece to the existing overflow drain to the sump and use the branch to supply the skimmer. In order to regulate the supply, a valve should be fitted below the tee.  Ensure that the pipe feeding the skimmer is of large enough diameter and that there is enough head to provide
the proper flow rate.

Andy,
D-D

[aquavista99]

I would be interested in seeing pictures of skimmer setups from people who use  gravity supply as well. Here are a few pictures I photographed today of my skimmer attached to Joel's 300 gallon Rubbermaid tub. The skimmer is a ER RC 500  with a Mag 7 feed pump. I have to clean the skimmer at leat two to three times a week. The fish load is very light and most SPS corals in the tub are small frags.

[Joel]

I think that there are multiple factors that can influence what is the best way to deliver water to a protein skimmer. Note that what I just said was what is the best way to deliver water to a protein skimmer, not what is the best way to remove nutrients from your aquarium or what will make the best use of your protein skimmer.

If this subject was as simple as, "what is the best way to get water into my protein skimmer to allow the protein skimmer to have the maximum benefit to my aquariums water?" the the answer would be, water that has been surface skimmed straight out of the aquarium and drained directly into the skimmer...period!

It is an absolute fact that the raw surface water is the most pollution concentrated portion of aquarium water in all aquariums. Draining water into a sump and then pumping it back into a skimmer decreases the concentration of the surface pollutants getting into the skimmer. Even if the protein skimmer feed pump is located in the first chamber of the sump that water from the aquarium is drained into, it still decreases the concentration of surface pollutants getting to the skimmer. When surface water is churned or disturbed, these pollutants return to the surface very quickly. A pump sitting on the bottom of a sump is going to miss a fair amount of them.

Now, that being said, this is not to say that other methods of water delivery to a protein skimmer are wrong. It's more a case of good, better and best.

There are many circumstances (more than room here will allow for) that will determine if this type of water delivery to your protein skimmer is the right thing to do. The immediate things that come to my mind are;

Recirculation type skimmers are probably the only type of skimmer where this is an option, perhaps old school counter current style with an air stone could too.

Can your skimmer handle that amount of water flow (GPH)?

Is this water volume (GPH) adequate for your size aquarium? Is it to slow (not enough GPH) Is it to fast - to short of dwell time?

Et Cetera.....

I'm certain that there are many more factors that will determine if this can or should be done on ones aquarium / protein skimmer. But I will say that if it is an option to directly feed your protein skimmer right out of the aquarium VIA a surface skimming over flow, this is the best option. Remember that nutrient export / removal is the # 1 priority of our water management systems. Directly feeding the most pollution concentrated water to your protein skimmer and allowing it to remove it before the water enters the next stage of filtration really decreases the load on the entire system. The more quickly & efficiently waste is remove from out water, the better the quality of our water and the longer the duration it will stay that way. These are not opinions, these are facts.

For what it's worth, I have the exact Euro Reef RC 500 protein skimmer that Tim has. I feed it directly from my tank VIA a surface skimmer box. Since doing so, the concentration of waste and the rate I collect it from the aquarium is noticeably greater than it was when it was fed by a pump located in my sump. In my situation, I do see an improvement in performance.


Joel

[aquavista99]

Very nice, informative post, Joel! It sounds like gravity supply would not be the best option for most smaller, non circulating skimmers. Do you know what method is used for the mega skimmers you see at public aquariums and zoos?  "When surface water is churned or disturbed, these pollutants return to the surface very quickly" also explains why the dirtiest water in any aquarium is always on the surface.  Would you mind posting a picture of your surface skimmer box?

[Joel]

My surface skimming box is par  with what just about everyone else has, Just a run of the mill built in O/F box with a durso type stand pipe. I run the 1" drain out of it & straight to the protein skimmer.

The improvement that I wish I could make would be to have a better & larger surface skimming box. I currently have the type with the "teeth" cut into it, mostly for live stock protection. A larger and just flat, level wall (box) for the water to fall over would be better for organic skin removal. With this tank, it's not an easy option to change, the box is built in.

 On that particular tank, I don't (intentionally) have a huge return pump so the amount of water flow going thru my P skimmer is right in the middle  to upper of desirable GPH for it's total system volume of water. (depending on who's formula you subscribe to)

I don't understand the recommendations about keeping the correct pressure, etc. of feed water flow. Recirc type skimmers are just a big tube with free flow water passing thru them, no pressure at all. I just throttle back the 1.5" drain to get the water level adjusted correctly and let the recirc pumps do the rest. (that's a little oversimplified but is the "jist" of it)

Tim, your correct that with smaller or non recerc type skimmers this would not be an option, pumping water from the earliest point in the sump or having the protein skimmer in the first chamber of the sump may be the next best option. I have only seen the equipment & filtration systems of a few public aquariums & Zoo's and recall that they were set up flooded sump with high pressure pumps feeding the skimmers & fluidized sand filters. These were not recirculating pumps and has been several years ago. At that time many were  using the RK2 filters that were high tech - cutting edge in the day. Now I'd call them just bigger versions of what many use on their aquariums now.

[aquavista99]

It is an absolute fact that the raw surface water is the most pollution concentrated portion of aquarium water in all aquariums. Draining water into a sump and then pumping it back into a skimmer decreases the concentration of the surface pollutants getting into the skimmer. Even if the protein skimmer feed pump is located in the first chamber of the sump that water from the aquarium is drained into, it still decreases the concentration of surface pollutants getting to the skimmer. When surface water is churned or disturbed, these pollutants return to the surface very quickly. A pump sitting on the bottom of a sump is going to miss a fair amount of them.

Maybe why my reef water is always so super clean is because whatever pollutants returns to the surface from my first chamber and escapes  the protein skimmer's feed pump is quickly consumed by the macro algae contained in my second chamber. I use a large amount of cheato in my second chamber of filtration, which grows on the surface of the water, most likely preventing the surface pollutants from returning to my reef aquarium. The end result is super clean water and colorful SPS corals. Even with using macro algae, my skimmer pulls out large amounts of nasty, dark skimmate everyday which is why I have no need to consider gravity supply at this time, even though it sounds like this could be an option since I run the same RC 500 skimmer as you. Again, thanks for the very informative reply, Joel! 

[Rob]

Here is my *opinion*.

I always recommend feed pumps over gravity feeds.
- you can better determine how much water you are feeding to the skimmer - want 300 gph, get a pump that will feed 300 gph
- the water is more consistent, there is no "burping" with a feed pump

I think that in the grand scheme of home aquariums, we are not dealing with that much water volume.  Most guys are turning their tanks over 10X+ an hour. Take a 200 gallon tank, you are looking at 2000 gph.  If the "dirty" water does not make it through the skimmer the first go round, it will likely make it through very shortly.

You could also take it a step further and make the argument that normal reef ready tanks still leave surface skim on the water.  If you get a chance, check out Antony Calfo's "Coast to Coast" overflow design.
Here is a link: http://www.reefcentral.com/forums/showthread.php?s=&threadid=473152&highlight=Calfo+style+overflow

Happy reading.

[Viggen]

I was always under the impression that turning a tank over 10x+ is a bad thing, that is if we are talking about the water going through the sump.  Sumps need a much slower rate especially the refuge's that many of you use.  With my w/d filters I only run around +/- 4x's a hr through them, my new tank will be closer to 5x's a hr with +/- 1x going to my skimmer.   

When feeding a pump off a overflow it's also not hard to determine how much flow you are getting.  But true, it does take a little more time then just buying a pump that does the gph you are looking for.  Add a gate valve & you can tune the flow to the skimmer quite easily but it does take a bit more work  



 

[Joel]

  If the "dirty" water does not make it through the skimmer the first go round, it will likely make it through very shortly.

This is an example of exactly what I was speaking of (and against). We want our systems to operate as efficiently as possible to remove waste from our water. Your correct that flow rate is very important but flow rates directly off our aquarium drain is very controllable The theory or opinion that the waste that our filters miss the first time thru isn't a major concern because the filter will get multiple other attempts at it is true. But this is not what is most ideal, it is a compromise. ( I'm not quoting Rob as saying that missed waste by our filter isn't a concern, I'm commenting on the implication)

If a filtration system is a less efficient design and takes many passes thru it to remove or brake down waste, the waste is aloud to be dissolved in the water longer thus have a more negative impact on the overall quality of the environment. In other words, the longer waste is aloud to remain in our water and brake down, the more harm it is causing to the aquarium.

Another consideration is just about all protein skimmers are influenced by the water level inside them. If the water level in the sump drops due to evaporation, the pump will have more gravity to fight against and as a result, the water level in the skimmer will drop due to less GPH causing it to no longer be adjusted to optimal setting. This can be solved by having a dedicated chamber for the skimmer or the skimmer feed pump that has a constant water level but few people have their system set up that way.

I'm sure we could go all day long about the good and bad about each method and both sides have some valid points. My point is that if it is an option to direct feed your skimmer, and it is done in a fashion that has proper water flow & proper surface skimming of the water, this is superior at waste removal than pumping water to the skimmer from the sump or elsewhere. I think that we all can agree that as raw as water we can supply to our skimmers, the better. We want to remove as much waste as possible before the water gets to other filtering apparatus. Anything and everything we can do to increase the efficacy in which  we remove waste from our systems, the better it is going to be for the overall health of the tank and it's inhabitants.

[aquavista99]

Here is my *opinion*.

I always recommend feed pumps over gravity feeds.
- you can better determine how much water you are feeding to the skimmer - want 300 gph, get a pump that will feed 300 gph
- the water is more consistent, there is no "burping" with a feed pump

Thanks for adding your opinion to this debate as well, Rob!  Both Chip and Jeff at EuroReef were pretty adamant about recommending the feed pump method to obtain better results as well when I purchased my skimmer a few years ago. I have been really impressed with the results I have obtained by using a feed pump on my skimmer. The only downside is increased energy costs and cleaning yet another pump every few months.

[Baggerhog]

Andy, nice info.  I dont want to be a pain, but is there a way to prove a generic drawing of the 'T' you're talking about.  i want to get this right the first time around. 

I would but to be honest I just dont know how to do that on the computer. I will ask Joe if he can draw a diagram.

I would also like to add that controlling the flow is simple if you are not running a wave or wavebox in your system. If you are and your tank is a dual overflow then one side drains when the water level is high on that end and then it switches to the other side. If you have a tank designed with dual overflows and your water resonates back and forth then it will be almost impossible to use direct gravity feed. The reason is your skimmer will pull air when the water level is low on that side and cause the water level in the chamber of your skimmer to flucuate. The skimmer will then have more air and burb as Rob said.

If you have constant even water flow through both overflows then it is easy to control and maintain a constant set amount of water flowing through your skimmer as Joel stated. The water level wont change like it may with a feed pump.

I did not direct feed my skimmer because I was running two wave boxes. I have since change my tank flow design and now wish I would have used 1 of my 6 one inch drains to feed the skimmer. I know I would be getting the dirtiest water and I would reduce the need to use a feed off of one of my snappers. For those running a seperate pump by direct feeding you will be reducing your electric bill by not having to run a feed pump. I am sure there is something to be said for that. This hobby is expensive enough as is why waste money. I wish I would have known my design now back then and I would be direct feeding.

[Amstar]

what if your skimmer needs (it says) 1100pgh to operate correctly.  how much does a 1" drain bring down to a skimmer if its gravits feed

[Joel]

what if your skimmer needs (it says) 1100pgh to operate correctly.  how much does a 1" drain bring down to a skimmer if its gravits feed

That doesn't sound like a recirculating skimmer, it is not an option to operate as a direct feed if this is the case.

[Viggen]

What skimmer is that?  Is it a NW skimmer?

Like Joel stated it doesn't sound like a RC/NW skimmer..... if it is a NW how big is the reaction chamber?  Must be HUGE

I think a 1 in drain does less then 800 gph but I forget the exact number

[aquavista99]

For what it's worth, I have the exact Euro Reef RC 500 protein skimmer that Tim has. I feed it directly from my tank VIA a surface skimmer box. Since doing so, the concentration of waste and the rate I collect it from the aquarium is noticeably greater than it was when it was fed by a pump located in my sump. In my situation, I do see an improvement in performance.

Although Joel and I have the exact same EuroReef RC 500 protein skimmers and the exact same 125 gallon sumps, the reason why direct feed should work better for Joel whereas a feed pump works better for me, is because the way we use our sumps, both built by Joel, are just the opposite. In my opinion, I think it would be difficult to use a feed pump on Joel's skimmer to get the best results based on how his sump is designed. If I recall, the place where your dirty water discharges into your 125 gallon sump is located on the opposite end of where your skimmer is located, approximately 6 feet away. The chamber where you would place your feed pump would be the third chamber in my 125 gallon sump, which means you would not be feeding your skimmer as dirty of water water since it would have to pass through your first chamber, then your second macro algae chamber before finally reaching the third chamber, which is where your return pump and skimmer feed pump would be located.

In my system, the dirtiest water is trapped in my first chamber, which is where my skimmer's feed pump is located as well. The water would then move into my second chamber, which is also filled with macro algae, then exits back to the aquarium via the return pump in my third chamber.

[Viggen]

he could just as easily throw a pump where the filter socks are & run a pump from there.  It's only 6ft of non vertical head pressure so the flow loss would be minimal......

[CoralBeauties]

If I direct feed my skimmer from the overflows is there a reason for a filter sock?  I would think that you could also do away with the filter sock and have one less thing to have to maintain.
Jeff

[aquavista99]

he could just as easily throw a pump where the filter socks are & run a pump from there.  It's only 6ft of non vertical head pressure so the flow loss would be minimal......

Very true, Gary. You would obtain better skimmer performance results if you place the feed pump in the first chamber as opposed to the third and final chamber.

[aquavista99]

If I direct feed my skimmer from the overflows is there a reason for a filter sock?  I would think that you could also do away with the filter sock and have one less thing to have to maintain.
Jeff

I would think the filter socks may also cut down on the splashing noise and filter whatever was missed by the skimmer, unless you have both overflows connected to the skimmer. Maybe the gravity/direct feed people may want to chime in as well?

[slandis3]

i am running my new reeflo 200 directly off the overflow well see how it works. so far its pulling a good amount of nasty stuff out. well se how it does when it breaks in

[Joel]

I still use a filter sock on the out flow side of my protein skimmer. Althought the skimmer does put lots of junk out, particulate matter still gets thru it and the sock catches it.