ATS... A Skimmer Performance Indicator?

[d2mini]

I was just thinking. Uh-oh :worried:

If you had both a skimmer and an algae turf scrubber, could one indicate the performance of the other?
In other words, lets say your ATS was producing, but maybe not all that much. And your skimmer was pretty consistent. Would this be an indication that your skimmer was sized correctly for your tank?
Now let's say you were harvesting from your ATS every few days, and your skimmer was still churning out lots of skim on a very consistent basis. Would this be an indication you could maybe use a more powerful skimmer?

On systems with just a skimmer, if you saw your skimmer being very consistent with almost no down time, you may think to yourself that an upgrade may be needed. But then you do that, and now your are getting very inconsistent skimming. What if you added an ATS instead? Maybe that would be enough to take up any nutrient overage that your current skimmer may be missing, without worry of ending up with a skimmer that is oversized.

I tried an ATS once and it just didn't work out. My skimmer was skimming well and there just didn't seem to be enough nutrients for the ATS to produce much of anything. So by the same token, I guess you could say the ATS told me my skimmer was performing well and was appropriately sized. Yes?

What are your thoughts on using an ATS to gauge skimmer performance?

 

[Lavoisier]

From several l studies I've looked at, the most our skimmers will do is about 30% removal of organics. I've never seen a study on ATS devices though I've used one for about a year and have installed one on my new build. My water parameters are much better and more stable since using the ATS. I think the best determinate will be water quality based on standard parameters--PO4, nitrates, nitrites, ORP, etc. I know there are a number of folks who are going skimmerless and using ATS only...:rolleye1:...but I'm not there yet! I would rather use both even if I'm being a bit redundant.

 

[DavidinGA]

I have a skimmer and ats on my 210gal. Skimmer pulls great and the ats grows good (clean it every 10-14 days). I can't really draw any conclusions because on top of the skimmer and ats I'm also vodka dosing, which could be why my skimmer pulls so hard...

 

[slief]

Here is my take and a long one at that.

Skimmers primarily remove dissolved solids. Food etc and some smaller dissolved nutrients before the stuff breaks down as well as some of the stuff that has already broken down. The scrubber primarily consumes nutrients that have already broken down. The skimmer provides benefits over and above the DOC removal and as such, I wouldn't run a system without a skimmer.

In retrospect, we are always striving for having a display that is free of nuisance algae and obviously nutrients are typically the root cause of that. This is where the ATS and or our refugiums come into play. Clearly, many of us have found that a great skimmer and even GFO alone isn't the entire answer or solution. The ATS and refugium provide an optimal environment for macro algae to outcompete the nuisance algae in our displays by growing algae under lighting better suited for macro growth so that it grows fast enough to consume the nutrients before algae can gain a foothold in our display. We then go in and remove the macro or much of it effectively exporting the nutrients it consumed and allow the cycle to repeat.

A refugium can be very efficient at removing those nutrients and outcompeting display for nutrients by growing macro's such as chaeto, Caulerpa or other algae including even GHA provided it is pruned on a very regular basis. The ATS on the other hand is a more compact environment and arguably more efficient than a refugium largely because of it's compact size, close proximity lighting and the type of algae it grows along with the regular needed cleaning intervals.

My mindset is that the display is the best indicator of whether you have enough nutrient exporters. I run two refugiums now. One with a DSB and a huge mass of chaeto that gets biweekly pruning. The second is a display refugium that has Caulerpa, GHA, some chaeto, other macro algae, soft coral etc. My display is presently free of any nuisance algae growth which coupled with my test results tells me my system is consuming enough nutrients to keep my display clean and healthy.

Unfortunately every system is different and many systems may be able to get away skimmerless when using an ATS. Personally, I'd never go there because I firmly believe there are other benefits of running a skimmer beyond just DOC export. I also believe ATS are a great addition and I've even considered adding one to my system. Heck, I still think about it and could see an ATS on my system in the future. The only thing that really holds me back is the fact that I don't have algae issues in my main display. The flip side to that is that I do have some GHA in my display refugium that I prune regularly and I'm sure that could be eliminated by an ATS. The GHA in my display refugium doesn't really bother me though. After all, isn't that one of the reason we run refugiums to begin with? To grow algae there instead of our displays?

Obviously there is a fine balance when it comes to nutrients and corals because a certain amount of nutrients are needed to keep our corals thriving. When you have a heavy fish population with heavy feedings, the skimmer, ATS, refugium and corals will ultimately create a balanced environment on their own in an established system. It just boils down to how much algae do you need to grow in your refugium and or ATS to keep it out of the main display baring in mind that you can only keep algae growing in those environments if there is enough nutrients to feed them. Thus they create a balance on their own given an optimal environment to flourish.

 

[d2mini]

Yeah, I would never go skimmerless.

Slief, i too had HA in my fuge, took over all my macros. Nothing in the DT.
Maybe because we have tangs in our main display and they keep it at bay???

From several l studies I've looked at, the most our skimmers will do is about 30% removal of organics. I've never seen a study on ATS devices though I've used one for about a year and have installed one on my new build. My water parameters are much better and more stable since using the ATS. I think the best determinate will be water quality based on standard parameters--PO4, nitrates, nitrites, ORP, etc. I know there are a number of folks who are going skimmerless and using ATS only...:rolleye1:...but I'm not there yet! I would rather use both even if I'm being a bit redundant.

True, I forgot about that whole 30% thing. So maybe with 70% left, the ATS shouldn't really be effected by a skimmer? Hmmm...

 

[reefgeezer]

Skimmers remove certain dissolved organics before they can decompose and add bio-available nutrients. An ATS binds bio-available nutrients that are removed when the algae is harvested. IMO, while they do different things, the a change in algae growth in the ATS could provide a clue about how the skimmer is working.

 

[slief]

Yeah, I would never go skimmerless.

Slief, i too had HA in my fuge, took over all my macros. Nothing in the DT.
Maybe because we have tangs in our main display and they keep it at bay???

I've wondered about that myself. In years past though, before my refugiums, I've had GHA despite having tangs. As such, I do think the refugiums are outcompeting the display for nutrients. On the flip side, if any macro started growing in the display, the amount would be small enough that I'm sure the tangs and or my foxface would make quick work of it along with my CUC. I truly feel that the refugiums and ATS work and work well. If properly sized, they can go a long way in reducing or eliminating nuisance algae growth from out main displays. Heck, algae growth on the glass is a great indicator. Since adding my refugiums, the algae growth on my displays viewing panes has dropped dramatically by about 75%. I used to have to clean my glass weekly if not more and now I let it go two weeks between cleanings. That's not to say there isn't some buildup during that time but it pales in comparison to what it was in years past.

That said, there are many tanks that had major nuisance algae issues which were resolved with the addition of an ATS. I've seen a couple first hand myself so I would say they certainly do work and work well.

 

[dkeller_nc]

Skimmers primarily remove dissolved solids. Food etc and some smaller dissolved nutrients before the stuff breaks down as well as some of the stuff that has already broken down. The scrubber primarily consumes nutrients that have already broken down. The skimmer provides benefits over and above the DOC removal and as such, I wouldn't run a system without a skimmer.

Expanding on this a bit -

A skimmer removes surface-active organic compounds, and also some particulate matter. It does this by two different mechanisms. The surface-active compounds, such as proteins, fatty acids, lipids and other complex organics bind to the air-water interface and thus create a stable foam head. Presuming that the skimmer is of sufficient size/efficiency for the tank and bio-load, it will continue to remove these compounds until their concentration in the water is below a certain point. Us scientists call this concentration the Critical Micelle Concentration, and while the CMC is different for different molecules, the overall effect is to remove surface active compounds down to a certain concentration, below which a stable foam head isn't produced.

The final organic carbon concentration in the tank water at the point that the skimmer no longer removes any additional material is a combined result of the concentration of certain types of organic molecules that aren't surface active, and the average CMC of the surface-active organic molecules. As an example, if one made up a saltwater sample with 2-3 weight percent acetic acid, virtually none will be removed by a skimmer because acetic acid isn't particularly surface active. On the other hand, if one made up a saltwater solution with 2-3 weight percent of detergent, very nearly all, but not 100%, of the detergent would be removed by the skimmer.

This is the source of the anecdote that a skimmer will "only remove 30% of the TOC" - the skimmer in the study removed all of the organics down to the average CMC of the components, and no more. If the starting point of the study had been a good deal more concentrated in organics (say, from a "dirty" tank that wasn't running GAC), then the percentage removed would've been much, much higher.

The second effect of a skimmer, particulate removal, is the result of a different physical process called "entrainment". Essentially, the skimmer will remove particulates below a certain size by trapping them in between the bubbles in a stable foam head. In the case of bacteria, removal is helped along because a lot of bacteria are also "sticky" and will adhere to a certain extent to an air-water interface.

An ATS does something entirely different - algae grow by adsorbing inorganic nutrients as they photosynthesize and add new plant tissue. These nutrients are primarily nitrate, phosphate and minor elements like potassium, with a bit of trace elements like iodine, iron, manganese, zinc, etc...). These types of compounds aren't removed directly by a skimmer at all - only indirectly by removing bacteria that are absorbing these nutrients as they reproduce.

So one can effectively manage certain organic contaminants with a skimmer directly, and indirectly manage inorganic nutrients by carbon dosing to encourage bacterial growth, and subsequently removing them by skimming. Those organic molecules that aren't surface active can be managed directly by removal with GAC, and also by the action of bacteria that break these organics down and absorb them as part of their growth cycle.

With an ATS, one can directly manage inorganic nutrients by growing and harvesting algae, and indirectly manage organic contaminants by the use of GAC. Trace element depletion by the growing algae can be managed by additions, or preferably, water changes.

In my opinion, there's probably little need to run both an ATS and a skimmer with carbon dosing, because they accomplish similar export functions by different mechanisms. Also in my opinion, running GAC with either nutrient removal strategy is important. For me, I'd rather use a skimmer because I don't have fish that require the algae as part of their diet, and maintaining a skimmer is, IMO, easy and also ensures that the dissolved gas concentrations in the tank water are in equilibrium with the atmosphere.

So there you have it - my $0.02.

 

[d2mini]

Great info dk, thank you for taking the time to type all that.

In my opinion, there's probably little need to run both an ATS and a skimmer with carbon dosing, because they accomplish similar export functions by different mechanisms. Also in my opinion, running GAC with either nutrient removal strategy is important. For me, I'd rather use a skimmer because I don't have fish that require the algae as part of their diet, and maintaining a skimmer is, IMO, easy and also ensures that the dissolved gas concentrations in the tank water are in equilibrium with the atmosphere.

But what if one is not carbon dosing?

 

[reefgeezer]

Expanding on this a bit...

Great explanation, thanks. Can GAC manage TOC level all by itself to the same level as might be expected from a decent skimmer? I ask because I believe that high dissolved organic levels can fuel Cyano and possibly even Dino's.

 

[dkeller_nc]

Great info dk, thank you for taking the time to type all that.

I type quickly - I hated it at the time, but I'm very glad my high school required every student to take Typing to graduate.

But what if one is not carbon dosing?

I guess my thought is: why would anyone not carbon dose? IMO, this is the single biggest innovation in reef husbandry since I started in 1990. To me, it's a bigger deal than propeller pumps, needlewheel skimmers, and LED lighting. The only thing that comes as a close second is the use of GFO and readily available coral food.

Both of these techniques (carbon dosing and GFO use) allows remarkable control of the two of the biggest irritations in long-term reef management: slowly rising nitrate and phosphate concentrations. In the 1990's, I remember that heroic water changes was just about the only solution, and even that wasn't much good in a heavily loaded tank.

 

[dkeller_nc]

Great explanation, thanks. Can GAC manage TOC level all by itself to the same level as might be expected from a decent skimmer? I ask because I believe that high dissolved organic levels can fuel Cyano and possibly even Dino's.

I would hazard a guess that the answer is "yes", but is probably not the most practical solution. Also keep in mind that GAC doesn't remove all types of organics. That said, it would be an interesting, albeit potentially expensive, experiment - keep a reef tank with nothing more than water circulation and GAC (and possibly GFO).

One thought about GAC - the common wisdom seems to be "replace GAC once a month". That may well be salient advice if one's major purpose is removal of water-yellowing compounds. But extrapolating from organics removal from waste streams would suggest that the carbon's saturated in far shorter time.

For example, I've been replacing the carbon in my 50 gallon cube once per week for the last couple of months as an experiment. This tank's equipped with an Apex, so I have a continuous pH record. When I change the carbon in the reactor, and do no other tank maintenance whatsoever, the pH in the tank increases by about 0.15 units within 20 minutes of putting the reactor back in service.

This is repeatable, though I've tried a number of different pre-treatments with the carbon to rule out the possibility of residual basic compounds from the activation process. My take on it is that the GAC is rapidly removing a good bit of organic acids from the water, and the pH increases as a result. Over the following week, the pH of the tank water at the same time of day gradually decreases day after day until it returns to pre-GAC-refresh levels.

I doubt that something like this is all that helpful for reefkeeping - our organisms seem to be a tough lot that can withstand quite a bit of difference from their native waters. But I do think it's interesting - a pH of less than 8.3 may not solely be caused by excess CO2 concentrations in our homes, and less-than-perfect gas exchange.

 

[reefgeezer]

I would hazard a guess that the answer is "yes", but is probably not the most practical solution...

Great explanation. Thank You.

 

[hart24601]

I guess my thought is: why would anyone not carbon dose? IMO, this is the single biggest innovation in reef husbandry since I started in 1990. To me, it's a bigger deal than propeller pumps, needlewheel skimmers, and LED lighting. The only thing that comes as a close second is the use of GFO and readily available coral food.

Both of these techniques (carbon dosing and GFO use) allows remarkable control of the two of the biggest irritations in long-term reef management: slowly rising nitrate and phosphate concentrations. In the 1990's, I remember that heroic water changes was just about the only solution, and even that wasn't much good in a heavily loaded tank.

+1, great write up dkeller.

 

[Big E]

This is the source of the anecdote that a skimmer will "only remove 30% of the TOC" - the skimmer in the study removed all of the organics down to the average CMC of the components, and no more. If the starting point of the study had been a good deal more concentrated in organics (say, from a "dirty" tank that wasn't running GAC), then the percentage removed would've been much, much higher.

I'm not sure which test you're referencing, but if it's the one below the percentages mentioned were only bacteria counts not % of organics.

http://www.advancedaquarist.com/2011/3/aafeature

Just want to clarify that as it's makes a huge difference in what people are talking about.

I never bought those conclusions as it's very easy to poke a ton of holes in that testing.
I'm not going to go there as the test still has some value, but you have to look beyond the limitations of that study.

I think you've done a good job covering how much other pre-nutrient fuel is taken out by the skimmer that the bacteria doesn't get.

As far as to the OP's question.........

I've always drastically oversized my skimmers and have never employed refugiums/scrubbers. I've never had any issues with nutrients being high unless my skimmer was undersized.

When my skimmers were too small or inefficient I had to carbon dose to make up the difference. Did that for 2 years.............I'm currently back to large oversize skimmer again without carbon dosing for the past year.

For a reference point I ran a Deltec AP703 which could handle heavily stocked 600g on a 160g total volume Sps dominant system. My PO4 was a consistent .03 and nitrates 0 for 7-8 years.

No other export tools were used.

 

[dkeller_nc]

Actually no - I was referring to this article and this follow-up. The modeling is still useful, but some of the physical explanations about what's happening could use some refinement.

 

[Big E]

Ok, thanks, I do remember those also..............agreed

 

[ksed]

That study was done using activated carbon and with out activated carbon.

Expanding on this a bit -

A skimmer removes surface-active organic compounds, and also some particulate matter. It does this by two different mechanisms. The surface-active compounds, such as proteins, fatty acids, lipids and other complex organics bind to the air-water interface and thus create a stable foam head. Presuming that the skimmer is of sufficient size/efficiency for the tank and bio-load, it will continue to remove these compounds until their concentration in the water is below a certain point. Us scientists call this concentration the Critical Micelle Concentration, and while the CMC is different for different molecules, the overall effect is to remove surface active compounds down to a certain concentration, below which a stable foam head isn't produced.

The final organic carbon concentration in the tank water at the point that the skimmer no longer removes any additional material is a combined result of the concentration of certain types of organic molecules that aren't surface active, and the average CMC of the surface-active organic molecules. As an example, if one made up a saltwater sample with 2-3 weight percent acetic acid, virtually none will be removed by a skimmer because acetic acid isn't particularly surface active. On the other hand, if one made up a saltwater solution with 2-3 weight percent of detergent, very nearly all, but not 100%, of the detergent would be removed by the skimmer.

This is the source of the anecdote that a skimmer will "only remove 30% of the TOC" - the skimmer in the study removed all of the organics down to the average CMC of the components, and no more. If the starting point of the study had been a good deal more concentrated in organics (say, from a "dirty" tank that wasn't running GAC), then the percentage removed would've been much, much higher.

The second effect of a skimmer, particulate removal, is the result of a different physical process called "entrainment". Essentially, the skimmer will remove particulates below a certain size by trapping them in between the bubbles in a stable foam head. In the case of bacteria, removal is helped along because a lot of bacteria are also "sticky" and will adhere to a certain extent to an air-water interface.

An ATS does something entirely different - algae grow by adsorbing inorganic nutrients as they photosynthesize and add new plant tissue. These nutrients are primarily nitrate, phosphate and minor elements like potassium, with a bit of trace elements like iodine, iron, manganese, zinc, etc...). These types of compounds aren't removed directly by a skimmer at all - only indirectly by removing bacteria that are absorbing these nutrients as they reproduce.

So one can effectively manage certain organic contaminants with a skimmer directly, and indirectly manage inorganic nutrients by carbon dosing to encourage bacterial growth, and subsequently removing them by skimming. Those organic molecules that aren't surface active can be managed directly by removal with GAC, and also by the action of bacteria that break these organics down and absorb them as part of their growth cycle.

With an ATS, one can directly manage inorganic nutrients by growing and harvesting algae, and indirectly manage organic contaminants by the use of GAC. Trace element depletion by the growing algae can be managed by additions, or preferably, water changes.

In my opinion, there's probably little need to run both an ATS and a skimmer with carbon dosing, because they accomplish similar export functions by different mechanisms. Also in my opinion, running GAC with either nutrient removal strategy is important. For me, I'd rather use a skimmer because I don't have fish that require the algae as part of their diet, and maintaining a skimmer is, IMO, easy and also ensures that the dissolved gas concentrations in the tank water are in equilibrium with the atmosphere.

So there you have it - my $0.02.

 

[ca1ore]

Yeah, I would never go skimmerless.

Slief, i too had HA in my fuge, took over all my macros. Nothing in the DT.
Maybe because we have tangs in our main display and they keep it at bay??

I have developed this theory over many years, fully unsupported by any scientific rigor, that controlling nutrients is only the first step in managing pest algae. Herbivores are the second step. I run a large skimmer, ATS, GAC and GFO (I don't carbon dose) and my nitrates and phosphates are unmeasurable on the hobbyist kits. Not a speck of GHA in my display, yet it grows like gangbusters on my ATS screen and did in my connected frag tank. Clearly there are enough nutrients to serve the algae. So why does it not also grow in the display; and no longer in the frag tank? Herbivores. I'm lucky in that my Tangs will eat GHA with enthusiasm. If I put a GHA infested frag plug into the main tank it is spotless within an hour. I've not always had Tangs that would do this though. Added a scopas to my frag tank, and now no GHA. Clearly low nutrients are important; if high, maybe even an army of Tangs couldn't keep up.