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For everyone who says to overskim...


malawian

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So I would think that many people, like me, at some point or another have to rely on information from somewhere else when setting up some part of their tanks. For me it was with my skimmer, it was my first "real" skimmer and I didnt know much about them so I had to look for outside help. One common theme was to oversize the skimmer so thats what I went with. Well trust me, you can go too big.

 

I went with a RO XS-160 skimmer, which BRS rated for about 120g. I thought, 75g tank, reasonably heavily stocked with heavy feeding, should be great. What I did not know, is that Coralvue rates this skimmer for 180g and more importantly they say that in a tank less than 100g, the skimmer may not work correctly and they explicitely recommend NOT to use the skimmer on tanks smaller than 90g. I really wish BRS would have included this information on their site. Of course, I found a couple of people with this skimmer on 75g tanks and they said it worked great (which means I can only imagine the stocking in those tanks).

 

Well the skimmer is a champ, but my tank cant maintain enough foam head. Through the course of learning by banging my head I have since learned about chamber sizes and neck sizes. The neck on an XS-160 is 4" wide and my tank cant maintain a foam head big enough to ever get skimmate into the cup.

 

The result? The skimmer is so strong it starts to pull trace elements out of the tank and it forms a thick foam (but not thick enough) and drops nitrate and phosphate to absolute 0 (which even makes some SPS unhappy and definitely makes all LPS/clams unhappy). But because that foam cant make it into the cup, it starts to break down into phosphate and nitrate and it seems to do so more or less all at once, so then phosphate and nitrate spike.

 

Moral of the story? You can go too big on a skimmer. Sure I knew that a skimmer rated for 400g probably wont work on a 6g pico but I didnt think there would be a problem at this size. I think the "over skim!" mentality came about when manufacturers were really over rating their skimmers so it wasnt so much of a mentality that you should get a skimmer intended for a tank larger than yours but just that whatever skimmer you were looking at isnt really intended for a tank its advertised for. But today, I think most manufacturers are better about this, BRS gives you a good idea about what it thinks the skimmer is really good for if you shop/research with them and if youre getting a Reef Octopus, look at Coralvue's site. I didnt even know about coralvue until I started trying to find solutions for this problem but they rate their skimmers according to light, normal and heavy load and also give warnings like the one for my skimmer.

 

TL;DR- You can get a skimmer that is too big, dont buy one thats too small but be very careful oversizing your skimmer.

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Try running it only a fraction of the time on a timer? Or every other week?

 

Agree sizing is an issue, I just wonder if there is a work-around.

 

E

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Sounds like the skimmer is sitting too high out of the water if it can't even make it into the cup. I'm using an SRO3000ext on a 180g and it's rated for a 400g light/250g heavy and I have no problem getting some serious nastiness out. You can also try running it for only half the day to allow more DOCs to build up.

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A 4" neck is definitely not too big for a 75g tank. I agree you probably don't have it submerged enough. A new tank is going to have a lot of trouble keeping the foam head on any skimmer anyway. The good thing about skimmers, is when enough material is available to be pulled out, the head will become large enough and push it into the cup. It just won't be constantly pushing foam into the cup.

 

You aren't going to be pulling trace elements out of the water - it a skimmer can't do that. Are you sure you have 0 phosphate? I am sure in 6 months from now you won't have anywhere near that.

 

For nitates, I have always had problems with very, very low nitrates and simply dose amino acids to keep them elevated at 2-3ppm. If you want nitrates and phosphates, just turn off your return pump when you feed and don't turn it back on for a half hour.

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There's got to be something else going on. The person I bought my 90 gallon from was running a roughly 1000 gallon rated deltec on it without any issues. Advanced aquarist did a skimmer research article some time back and they basically concluded that there's no way to overskim because skimmer efficiency isn't anywhere close to 100%. Basically the only detriment from running a grossly oversized skimmer was the addition of excess heat into the tank, or diluting your elements if you are skimming too wet.

 

Are you running biopellets or another carbon source?

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I am running biopellets

I have run the skimmer everywhere from 6.5-12" deep and everything inbetween (recommended is 8-9.5)

Tank is not new, has been up for more than a year

Phosphate is between .02-.04 ppm and Nitrate is undetectable (less than .06 ppm)

 

 

I have tried EVERYTHING to get this skimmer to work well and nothing works. Like I said, the skimmer does work, it just cant produce enough foam to get into the cup no matter how I set it, shallow or deep, high internal level or low internal level. The rep at Coralvue said this skimmer probably simply will not work on a tank my size. Now if I had a big predator tank where my bioload was huge, then maybe, but with a more reasonable bioload no.

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I am running biopellets

I have run the skimmer everywhere from 6.5-12" deep and everything inbetween (recommended is 8-9.5)

Tank is not new, has been up for more than a year

Phosphate is between .02-.04 ppm and Nitrate is undetectable (less than .06 ppm)

 

 

I have tried EVERYTHING to get this skimmer to work well and nothing works. Like I said, the skimmer does work, it just cant produce enough foam to get into the cup no matter how I set it, shallow or deep, high internal level or low internal level. The rep at Coralvue said this skimmer probably simply will not work on a tank my size. Now if I had a big predator tank where my bioload was huge, then maybe, but with a more reasonable bioload no.

 

Well 0.02-0.04ppm phosphate certainly isn't 0 and is nothing to worry about :) - that is more than enough phosphate for any coral, and even a little bit of algae. You don't need to worry about that until you are well, well below 0.01ppm. Your tank shouldn't be too "clean" for a skimmer that size.

 

I really don't think a 4" neck on a 75g is too much - my 20g tall uses a 3.5" neck and I get foam all day long on it - even restricting airflow through a huge (Tennis ball can) silencer and raising it 1" higher than suggested. Are you sure everything is alright with the pump and it is sucking enough air? Can you take a picture of the lower half of the skimmer in action along with a second picture of the neck? If the foam isn't thick enough, it could be a problem with the pump or an obstruction somewhere in the airline or venturi. If the tank is a year old, there should be more than enough junk to get the skimmer to get something into the cup.

 

For reference, in my tank I only have 2 clowns and a sixline with phosphates exactly the same as yours but with a little more nitrate (from AAs, if I didn't dose they would be around the same) and my skimmer's neck is only 1/2" smaller on a tank almost 1/4 the size. I've been getting constant foam for over a year out of it and my bioload is probably smaller than yours.

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If anyone can help me get this thing working I will worship the ground you walk on. I am seriously at my wits end with this skimmer. Ive got too much time and money in this tank for it to fail and I cant afford a new skimmer. This skimmer cost me a fortune and im about ready for a nervous breakdown.

 

This is the latest iteration of what Im trying. The skimmate in the cup I got from letting it skim for a while, then raising the internal water level quickly so it makes it all over flow then turn it back down. I dont normally do this but its the only way I can get anything in the cup at all right now and I have to do SOMETHING.

 

Currently skimmer is in about 10" of water and im putting the internal level just a few inches below the top of the neck. Before this I tried same sump depth but with the water level waaay down, like inside the skimmer body, that didnt work. Then I tried with the internal level somewhere just above the start of the neck, that ALMOST worked but still no. no skimmate after 3 days in that position. Everything I try I leave it there for a decent period of time to see if it will work, nothing ever does.

 

As for air intake, ive cleaned the intake tube with piping hot RODI water and the venturi is clean and in place. As you can see, it definitely pumps a decent bit of bubbles into the body.

 

Ive tried so many things I cant help but think the coralvue guy is right but if you guys can help me get this thing work...a very litterally might cry for joy.

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I'm not sure if you've overlooked a very simply possibility. You haven't mentioned how long the skimmer has been running. I've read that skimmers can take up to 3-4 weeks to start producing really nice foam and skimmate.



also, keep your hands out of the tank as the oils from your hands will dramatically reduce the ability to create a foam head

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I'm not sure if you've overlooked a very simply possibility. You haven't mentioned how long the skimmer has been running. I've read that skimmers can take up to 3-4 weeks to start producing really nice foam and skimmate.

 

also, keep your hands out of the tank as the oils from your hands will dramatically reduce the ability to create a foam head

about 2.5 months in the tank, not once has it made actual skimmate. And I do know that oils affect the skimmate production and after some foods for example I notice the foam dies down but it comes back within a few hours but never enough to get skimmate into the cup.

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about 2.5 months in the tank, not once has it made actual skimmate. And I do know that oils affect the skimmate production and after some foods for example I notice the foam dies down but it comes back within a few hours but never enough to get skimmate into the cup.

 

that's really strange. it really seems like you've covered all the basics. The only thing that i could think of would be something wrong with the pump not moving enough air and water... but i am in no way close to an expert on pumps

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Its hard to tell from your pictures where the "line" between the short-lived bubbles and the long-lived foam is, but it appears to be about a 1.5-2" below the neck - which would be a little too low for a skimmer that big on a smaller tank. Here is what I would suggest after seeing the pictures:

  1. Turn off the skimmer for a few minutes.
  2. Turn it back on and let it run for about 2-3 minutes - enough to fill up without producing any real long lasting foam.
  3. Adjust the skimmer so the "short lived" bubbles to come up about 1.5" into the neck, maybe even a bit higher. High enough that when you look through the side of the collection cup, you can see about 1/2" of bubbles.
  4. Let it sit like that for at least 3-4 days and adjust from there.

It seems the problem is you aren't generating enough "long lasting" foam to push it up above the top of the neck before they pop with how it is currently tuned. It is going to take a while to fill up a cup that big on a skimmer that big with just 75g. I wouldn't be surprised if you can get 7-14 days without having to empty the cup.

 

I would try to get it skimming fairly wet with a weak-tea colored skimmate and then slowly turn it back instead of trying to get it skimming dry right off the bat.

 

When you turn the effluent on your skimmer down as low as it goes, you can overflow the skimmer right? If you cant - then there is a problem or the skimmer needs to be in deeper water. As long as you can overflow the skimmer, you can make it skim on your tank.

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Its hard to tell from your pictures where the "line" between the short-lived bubbles and the long-lived foam is, but it appears to be about a 1.5-2" below the neck - which would be a little too low for a skimmer that big on a smaller tank. Here is what I would suggest after seeing the pictures:

  1. Turn off the skimmer for a few minutes.
  2. Turn it back on and let it run for about 2-3 minutes - enough to fill up without producing any real long lasting foam.
  3. Adjust the skimmer so the "short lived" bubbles to come up about 1.5" into the neck, maybe even a bit higher. High enough that when you look through the side of the collection cup, you can see about 1/2" of bubbles.
  4. Let it sit like that for at least 3-4 days and adjust from there.

It seems the problem is you aren't generating enough "long lasting" foam to push it up above the top of the neck before they pop with how it is currently tuned. It is going to take a while to fill up a cup that big on a skimmer that big with just 75g. I wouldn't be surprised if you can get 7-14 days without having to empty the cup.

 

I would try to get it skimming fairly wet with a weak-tea colored skimmate and then slowly turn it back instead of trying to get it skimming dry right off the bat.

 

When you turn the effluent on your skimmer down as low as it goes, you can overflow the skimmer right? If you cant - then there is a problem or the skimmer needs to be in deeper water. As long as you can overflow the skimmer, you can make it skim on your tank.

 

Wet or dry...I dont care I want skimmate! any skimmate! :(

 

Now Im not 100% clear on your instructions. So I dont know about on other skimmers but I can see a line where below it is bubbles in water and above it is just bubbles. Where should that line be? Are you saying to put that line about a half inch above the bottom of the skimmer cup? I will say I have tried it previously with pretty high water lines like that with pretty lame results still. I will try again though (ive probably not had it right there).

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masterbuilder

Seems the consensus is that its very difficult if not impossible to over-skim in our hobbyist systems. Search the net long enough and you can find an expert that says just about anything you want.

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Wet or dry...I dont care I want skimmate! any skimmate! :(

 

Now Im not 100% clear on your instructions. So I dont know about on other skimmers but I can see a line where below it is bubbles in water and above it is just bubbles. Where should that line be? Are you saying to put that line about a half inch above the bottom of the skimmer cup? I will say I have tried it previously with pretty high water lines like that with pretty lame results still. I will try again though (ive probably not had it right there).

 

I mean once the skimmer has been on for 2-3 minutes, literally whatever bubbles are there should be up into the neck, about 0.5" above the bottom of the cup when looking through the side (ususally 1.5" or so above start of neck). Turn it on, let it warm up for a minute or two, then adjust it so that when you look through the side of the cup, you see bubbles.

 

The point of only having it on for a couple mintues is so that no "long lasting" foam is produced (the stuff that actually gets pushed into the cup) and you can accurately adjust it. If you are adjusting your skimmer after it has been on for a few days, it's much harder to tell where that "line" is and why you typically only make very fine-tuning adjustments when it has been on constantly.

 

If you are able to overflow your skimmer by closing down the gate valve, you can make it skim.

 

Edit: Take a picture immediately after you adjust it (don't wait more than 5 minutes after the skimmer has been on to take the picture) and we can tell you if you have it right. If you wait more than a few minutes after turning the skimmer on, telling where that "line" is is much more difficult.

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Seems the consensus is that its very difficult if not impossible to over-skim in our hobbyist systems. Search the net long enough and you can find an expert that says just about anything you want.

 

The expert I spoke to were a pair of reps at coralvue, its not like I fished for an answer that made my $325 purchase useless. Like I said, Coralvue themselves specifically says NOT to use this on tanks smaller than 90g. And this is with more than 2 months of trying everything to get this skimmer to work well. If I can get it to work, Ill happily eat my words (instead of eating $325 I dont have to waste), though Ive not gotten it to work so far.

 

I mean once the skimmer has been on for 2-3 minutes, literally whatever bubbles are there should be up into the neck, about 0.5" above the bottom of the cup when looking through the side (ususally 1.5" or so above start of neck). Turn it on, let it warm up for a minute or two, then adjust it so that when you look through the side of the cup, you see bubbles.

 

The point of only having it on for a couple mintues is so that no "long lasting" foam is produced (the stuff that actually gets pushed into the cup) and you can accurately adjust it. If you are adjusting your skimmer after it has been on for a few days, it's much harder to tell where that "line" is and why you typically only make very fine-tuning adjustments when it has been on constantly.

 

If you are able to overflow your skimmer by closing down the gate valve, you can make it skim.

 

Edit: Take a picture immediately after you adjust it (don't wait more than 5 minutes after the skimmer has been on to take the picture) and we can tell you if you have it right. If you wait more than a few minutes after turning the skimmer on, telling where that "line" is is much more difficult.

 

Ok I know what youre saying. I did get some skimmate last night, but for the wrong reasons. I put in a brand new filter sock and it immediately went apeshit and overflowed. Its back to normal this morning. I will set it and take a picture when I get home today. Im pretty sure I can make it overflow, even at much lower water levels than what I have it at.Also, to help I may raise the water level even more, its at 10" right now (recommended 8-9.5) but I may bring it up to get it just below or on the outflow pipe. The more flow through the skimmer the more stuff skimmed right (like the most foam possible)? So if I can raise the water level as much as possible that should help I would think. The guy at BRS trying to help me said something similar, he said to put the water line somewhere in the middle of the neck which is pretty close to what you're saying too.

 

I will say, I have tried setting it high like this before. What seems to happen is there is not enough space in the neck for a thick head to form and bubbles just pop before they get over the edge. I dont know exactly where I tried it before or for how long so I will try this.

 

 

Yes, overskim! Aside from not having a tuned or broken in skimmer... You have a good problem to have. It means you can stock more heavily or feed more heavily. Both of which are desirable. Given that your skimmer is working properly. I really don't like that idea. If your skimmer has 'almost' skimmate. Thick with nutrients and toxins, it's almost in the cup but not,,, then the skimmer turns off. And all that concentrated 'almost' skimmate gets flushed back into the system.

 

That was my thinking as well. Also it seems like even if this werent an issue then there would be some fluctuation in parameters, if not a pretty significant one.

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Well..if you can't get it working, it's in your favor that you should be able to resell this skimmer for $275 easily or trade someone for a slightly smaller one that may be looking to upgrade. It's only 2 months old, it's a reef octopus which is IMO is as good as any other skimmer if not better. Mistakes in this hobby can be expensive.. i listened to everyone who said I NEEDED 250w halides over my 180g tank and proceeded to fry a lot of coral. I'm now running 150w bulbs which required me to buy new ballasts and sell off the 250w selectables for a loss after only a few months of use. I'm glad I did though because this tank is impressive. When you get comments from seasoned veterans in the hobby about your colors & growth, you're doing somethin right.. aside from it being young, only a year on the SPS growth, it competes with the best of them.



62E1ECB4-B07F-4C41-A0DF-326E22CCEE78_zps

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...The more flow through the skimmer the more stuff skimmed right (like the most foam possible)? ...

 

 

...I will say, I have tried setting it high like this before. What seems to happen is there is not enough space in the neck for a thick head to form and bubbles just pop before they get over the edge. I dont know exactly where I tried it before or for how long so I will try this....

 

More flow through skimmer !== more stuff skimmed.

 

The efficiency of the skimmer has to do with contact time, velocity, and bubble size. There is a sweet spot on every skimmer where it will be most efficient in a given amount of volume with a given bioload. I would try and keep the skimmer right around where they suggest. As long as you can make the skimmer overflow by closing down the gate/adjustment valve, there is enough water.

 

For part 2, you have to find the sweet spot between where they pop before getting over the edge and and being too high. Set it the way I and BRS suggested (no need for pics if you understand) and let it run for 3 or 4 days. You may not get ANY skimmate for a few days anyway if the bioload is really light. Once you let it run for half a week or so, then start moving the water level up/down without turning the skimmer off by no more than 1/2" at a time. When you adjust it, let it go for another 2 or 3 days before changing anything.

 

Skimmers should be dialed in slowly over time to ensure it is at the perfect level. A skimmer adjusted to be perfect one day after turning it on doens't mean it won't be all wrong after running for a week. I try to very roughly adjust mine when I clean it and then dial it in over the course of a couple weeks. Once it is dialed in, I don't touch anything even if it looks off or low for a couple of days. Even if I get no skimmate for half a week - no big deal.

 

I think the problem is you keep re-adjusting it before your changes have a chance to fully set in. it takes time. 2.5 months and the skimmer is barely broken in yet, it'll probably take a couple weeks to get it right. Stop making big changes and go very slowly - and don't keep changing the water level.

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biocubedatx

There's got to be something else going on. The person I bought my 90 gallon from was running a roughly 1000 gallon rated deltec on it without any issues. Advanced aquarist did a skimmer research article some time back and they basically concluded that there's no way to overskim because skimmer efficiency isn't anywhere close to 100%. Basically the only detriment from running a grossly oversized skimmer was the addition of excess heat into the tank, or diluting your elements if you are skimming too wet.

 

Are you running biopellets or another carbon source?

Its actually a reef octopus sitting on my frag system. 34 gallon frag display (neo nano), 29 gallon bio cube with 10 RTA and 2 ww clowns, and the 75 gallon sump. All pushed off a mag 18 manifold. This skimmer is a boss, photos show it in a 75 gallon diy sump I designed.

 

WTA7xXr.jpg

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I cleaned that yesterday btw

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ok with the water level thing in mind I should reduce water level back to the recommended 8-9.5?

 

second, again with the water level thing in mind, I turn off my return pump to feed the tank. There is no siphon backflow on the returns but still a bit of water drains down into the sump and raises the water level a bit. maybe by an inch-inch and a half. is that ok? fixing that issue is may be possible but definitely not easy at all and I may not be able to eliminate it. give me your thoughts on that.

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masterbuilder

Malawian,

 

Not wanting to debate the overskimming. You know the old saying...opinions are like a$$&oles...we all have one :D.

 

BUT...

 

If I understand what you are saying....your skimmer has never produced any skimmate. If that's the case then I don't understand how its overskimming your tank. Just bubbling around in the neck isn't removing anything....is it? Something must be wrong with the skimmer or how its adjusted. Maybe?????

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Water level in the sump needs to remain constant while the skimmer is running. If you turn off the return pump and the water level rises, then you're gonna overflow the cup.

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Just bubbling around in the neck isn't removing anything....is it? Something must be wrong with the skimmer or how its adjusted. Maybe?????

 

Thats the biggest problem, if the foam never makes it to the cup it will eventually break down, "rot" so to speak, in the way it would normally in your tank and turn into just phosphates and nitrates. If its not in the cup its still "in" the tank, its connected to the same water and all those nutrients eventually make it back into the water column.

 

Additionally, I suspect that this breakdown into just nutrients happens more or less all at once (or very quickly). The result is that phosphate and nitrate go way down, then go way up when the foam breaks down. This is just a theory because of course I dont do hourly phosphate and nitrate tests. At the very least, I can promise you that if the foam doesnt make it into the cup it will eventually break down into phosphate and nitrate.

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Yes, overskim! Aside from not having a tuned or broken in skimmer... You have a good problem to have. It means you can stock more heavily or feed more heavily. Both of which are desirable. Given that your skimmer is working properly. I really don't like that idea. If your skimmer has 'almost' skimmate. Thick with nutrients and toxins, it's almost in the cup but not,,, then the skimmer turns off. And all that concentrated 'almost' skimmate gets flushed back into the system.

 

Yeah no doubt! That is why I love running an "oversized" skimmer. I ran one rated for up to 210 on my 70g without issue, if I wasn't planning to use that skimmer for something else I would be running it on my 40B as well. A skimmer won't skim if it doesn't have something to skim out..... FEED or get more fish :) A big skimmer and biopellets with low bioload is a disaster waiting to happen anyway.

 

 

Thats the biggest problem, if the foam never makes it to the cup it will eventually break down, "rot" so to speak, in the way it would normally in your tank and turn into just phosphates and nitrates. If its not in the cup its still "in" the tank, its connected to the same water and all those nutrients eventually make it back into the water column.

 

Adjust the water level inside the skimmer if it isn't making it into the cup, you should be able to tune it to run straight SW into the cup if you want let alone any bubbly mess it can produce, it just takes some adjusting and patience. Put it in the amount of water RO suggests, adjust the water level inside, feed and watch it do its thing.

 

 

 

 

 

Also it isn't possible to overskim. No skimmer on the market is capable of skimming out anything that isn't there to be removed. You can run an oversized skimmer which will allow you to feed and stock at higher levels then normally suggested for your tank, but you really can't over skim ;) Running a massively over sized skimmer and feeding a couple small fish every few days is pointless and not what people recommend over sized skimmers for. The larger the skimmer the more it needs to have to be able to be skimmed out to be able to work the most effectively IMO. I'd really suggest try feeding more and see if that helps over the next week or so, between your skimmer size and biopellets it shouldn't be a problem with your current levels anyway.

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ok with the water level thing in mind I should reduce water level back to the recommended 8-9.5?

 

second, again with the water level thing in mind, I turn off my return pump to feed the tank. There is no siphon backflow on the returns but still a bit of water drains down into the sump and raises the water level a bit. maybe by an inch-inch and a half. is that ok? fixing that issue is may be possible but definitely not easy at all and I may not be able to eliminate it. give me your thoughts on that.

 

Stop moving the water level around and you will be able to dial it in. If you are within an inch of the recomended level, it'll be fine. Yes, 8-9.5 is optimal, but 7-10.5 will work too. As long as you can overflow it by closign the valve, there is enough water.

 

If your skimmer chamber in your sump has a fluctuting water level that changes every time you feed, NO skimmer will work regardless of it's size since it'll overflow everytime the level rises. You need to adjust your setup so the water level doesn't change every time you feed - or just leave the return pump on when you feed. I've never had any problems with feeding with my MP10 on full blast and my return pump on.

 

If you don't fix the fluctuating level in your sump - no skimmer (except recirc) will ever work for you. If you can't fix the fluctuating water level, you need to get a recirculating skimmer that doesn't rely on a constant water level. You have to fix one - otherwise it'll never work.

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