Studies on the effects of protein skimming

[JasonJones]

I just finished reading two interesting articles on protein skimming published in Advanced Aquarist in 2009 and 2010. I wanted to share those here and share some summaries for those who do not want to read through the entire articles, they are very long.

http://www.advanceda...09/1/aafeature2

http://www.advanceda...010/1/aafeature

Summary:

The studies focus on the removal of total organic compounds (TOC) in sea water.

The initial test uses four skimmer:

- Euro Reef CS80 Needlewheel

- Precision Marine ES100 Venturi

- Precision Marine AP264 airstone

- AETech ETSS Evolution 500 Downdraft

The second test compares 7 skimmers:

- Euro Reef CS80 Needlewheel

-Precision Marine ES100 Venturi

- Precision Marine AP264 airstone

- AETech ETSS Evolution 500 Downdraft

-Royal Exclusive 170 Cone

- Bubble King Mini 160

- Reef Octopus 150

Conclusions:

- No skimmer removes more than 35% of the TOC, "leading to the conclusion that bubbles are really not a very effective medium for organic nutrient removal" (may have other benefits, e.g. oxygenation).

- Price to Performance Chart (not sure how to embed the chart under our forum's rules)

http://www.advanceda...g/image_preview

- "Protein skimmers appear to have a much larger variation in their prices than they do in their ability to remove TOC from aquarium water."

- The Bubble King and Royal Exclusive cone were the only skimmers to exceed 30% TOC removal, both around 35%

- "Recent design innovations like bubble plates, conical sides, or pinwheel impellers do not seem to impact significantly on either rate of TOC removal or amount of TOC removed, at least for the skimmers tested. Thus, skimmer manufacturer claims about enhanced organic removal capabilities should be met with skepticism in the absence of compelling and quantitative TOC removal data."

Personal Notes:

Like most things in this hobby, the science does not always match with manufactures claims.

[pbnj]

I only skim 12 hours/day (9:00am-9:00pm).

[JasonJones]

Can you provide more info? Specifically, why you have chosen to adopt this methodology and what benefits you believe are derived from this approach.

[pbnj]

http://petersfishtank.com/?page_id=12#w.ptskim

[subsea]

I run skimmerless and have done so for more than 10 years. I read the above link and found it informative. The two arguments that I heard on going skimmerless were yellow water and nuisance microalgae. I say carbon solves yellow water and several other chemical problems that are not removed by protein skimming. With respect to nuisance microalgae, I use herbivores to some extent. I prefer using micro fauna and fauna in mud filters and deep sand beds to recycle nutriants. I also use macroalgae (seaweed) in refugiums to remove nutriants. Nutriant export and nutriant recycling both happen in the refugium.

[JasonJones]

Main info taken from the link Pat posted:

"The skimmer takes out carbon (TOC) and bacteria. Both of these are food sources for corals and fish. Many skimmerless tanks have better polyp extension and growth rates. The problem is, these tanks can also have yellow water, turbidity (cloudiness) and nuisance algae problems. I have even had phytoplankton blooms (green water) in skimmerless reef tanks. Until we find a better way, a compromise between a natural and mechanical system is the safe route. Shutting the skimmer off half of the time is a good place to start. If conditions get better or worse, you know which direction to go; if they stay the same, it still confirms the limitation of protein skimming. Then you start to think if it was really worth it to upgrade your skimmer the last two times I don’t see a benefit in any schedule other than 12 hrs on, 12 hrs off."

[subsea]

pbnj posted the link. I do have access to more information, however, I think that more data is not required.

Many methods work. Skimmerless works for me.

Several years ago, Erick Boreman and I shared a plane ride from Pittsburg to Houston. He is a knowlegable scientist with a doctarate and several books to his name. His reason for using protein skimmers is for insurance. He is in 100% agreement with skimmerless operations.

Patrick

[Woods]

Subsea (Patrick), PBNJ is also named Patrick or Pat. Hence the confusion, you are both Patricks :-).

By the way, the Hippos, I got from you are all doing fantastic!!! I kept 3 for my 180g and sold or traded the other 3 to family and friends. LIke you, I run skimmerless with a Refugium w/ MacroAlgae and 5 inch Deep Sandbed. Tank has been up for 6 months without any algae or Cyano outbreaks.

[JasonJones]

PBNJ is also Pat, confusing with multiples!

I agree, many methods work in this hobby when people understand their benefits and limitations. I have run several tanks over the years that were skimmerless and had very few water changes, but ran exceptionally well. An old 29g comes to mind that I loved.

I was hoping the original post would help people better understand the role and limitations of skimmers and manufacturers claims. Sometimes in this hobby it is easy to forget the science and instead focus on the current internet trends and manufacturers claims.

[pbnj]

PBNJ is also Pat, confusing with multiples!

OK, now I'm really going to confuse you....my legal name is Pasquale, but people call me Pat.

[subsea]

Subsea (Patrick), PBNJ is also named Patrick or Pat. Hence the confusion, you are both Patricks :-).

By the way, the Hippos, I got from you are all doing fantastic!!! I kept 3 for my 180g and sold or traded the other 3 to family and friends. LIke you, I run skimmerless with a Refugium w/ MacroAlgae and 5 inch Deep Sandbed. Tank has been up for 6 months without any algae or Cyano outbreaks.

Thanks for the clarification on the double Patrick. I think that we should have a party of St Patrick's Day.

Glad to hear about the "School of Hippoes" doing well in your system. Between the six Hippoes, they eat one pound of seaweed a week. As my seaweed production levels dropped with reduced temperature and sunlight intensity, I knew they had to go. I am glad they ae doing well. I will be ordering some seaweed and refugium kits from http://live-plants.com/ shortly after Christmas. There selection of plants is limited during these winter months. If you are interested, I'll let you know something after I talk to Russ. The shipping is $14 flat rate.

[+KimP]

This has been an interesting read. Thanks for posting, and for summarizing the articles I've gone back and forth over the years on whether to run my skimmer or not.

[PeeperKeeper]

This may be a dumb question, but if the skimmers only remove at most 35% of the TOC, what is the concern with running them 24/7? If they were taking out close to 100% or even 75% I would understand the concern with "overskimming" but why worry about it when they aren't that efficient anyway?

[JasonJones]

Interesting question. I think part of the answer lies in that while they may be inefficient in removing TOCs, they also remove such things as bacteria and plankton. Turning them off at nights leaves these things in the water when the corals are more active feeding.

Another interesting and related bit of information from an article on bacteria count in aquariums relating to carbon dosing. http://www.advanceda...011/3/aafeature

"Conclusions

The preliminary studies described herein document, for the first time, the modulation of water column bacteria population in reef tank water as a consequence of either (a) carbon source addition or (b) mechanical filtration (GAC, skimming). This information bears on the Carbon Dosing hypothesis for nutrient removal in marine aquaria.

Aquaria subjected to active filtration via skimming present water column bacteria populations that are approximately 1/10 of those observed on natural reefs. The consequences of this disparity on the long-term health of the tank's livestock are not known. How do reef tank organisms adapt to such a bacteria-deficient environment? Is the whole food web in an aquarium perturbed, or are there compensatory mechanisms that maintain an appropriate energy transduction through all of the trophic levels? Is "old tank syndrome" related to possible nutritional deficiencies stemming from this bacteria "gap"? Alternatively, could "old tank syndrome" be symptomatic of a gradual decrease of bacterial diversity as a consequence of selective skimmer-based removal of only bubble-susceptible bacteria? At present, it is not possible to go beyond speculation on these points - further research is needed.

On the other hand, our studies have shown that bacterial growth appears to be carbon limited in reef aquarium water. However, there is a demonstrable difference between reef tank water in an active reef tank, and reef tank water removed from the tank. In the latter case, bacteria consumers are largely absent, and so fueling bacteria growth via carbon addition translates to rapid and large increases in bacteria population. In an active reef tank, however, this population increase is not manifest, presumably because active predation keeps the overall level in check. Thus, the highly dynamic nature of bacteria populations in the water column of reef aquaria is highlighted by these studies. From a different perspective, the bacteria population in a reef tank seems to act as a buffer to help dissipate the otherwise potentially serious negative consequences of (inadvertent?) tank pollution via rapid carbon addition, at least perhaps up to a saturation point.

Finally, mechanical filtration in the form of skimming but not GAC does provide an effective means of bacteria export, at least up to a point. It appears likely that some types of bacteria are indeed "skimmable", but others are not. Thus, skimming inadvertently provides severe (?) evolutionary pressure to skew the tank's resident water column bacteria population to favor the "non-skimmable" cohort.

The bottom line with respect to the carbon dosing hypothesis is clear; the basic tenets of this theory appear to hold up to experimental scrutiny; carbon dosing does increase water column bacteria populations, and skimming does remove some bacteria with their attendant nutrient loads. Thus, the underlying science behind this approach to nutrient export appears valid."

I feel like this thread needs to be updated with some information on the good effects of skimming...

[subsea]

With respect to skimmerless operation, when lights are off pH and dissolved oxygen drop. Without sufficiant turbulance of the surface interface betwwen air and water it is easily possible to kill fisd at night. I use a surface skimmer to releave the surface tension on the water. This surface skimmer provides the water for the refugium. Also as an aid to pH stability, the macro in the refugium is on a reverse photoperiod.

[pbnj]

Because I only skim during the day, the bulk of my alkalinity is dosed when the skimmer/lights are off, thus maintaining the pH. Mine never drops below 7.9.

[JasonJones]

Just thought I would add this that I recently found:

Mr. Wilson on Skimming Part-Time

The skimmer takes out carbon (TOC) and bacteria. Both of these are food sources for corals and fish. Many skimmerless tanks have better polyp extension and growth rates. The problem is, these tanks can also have yellow water, turbidity (cloudiness) and nuisance algae problems. I have even had phytoplankton blooms (green water) in skimmerless reef tanks. Until we find a better way, a compromise between a natural and mechanical system is the safe route. Shutting the skimmer off half of the time is a good place to start. If conditions get better or worse, you know which direction to go; if they stay the same, it still confirms the limitation of protein skimming. Then you start to think if it was really worth it to upgrade your skimmer the last two times I don’t see a benefit in any schedule other than 12 hrs on, 12 hrs off.

So now that we have decided how long to shut it down for (12 hrs/day), we need to decide on the best time. The fish and corals are most active during the day during photosynthesis, and at night the corals open their feeding tentacles to collect the plankton that come out when the lights go out. Shutting the skimmer off at night seems to be the smart move, and if it influences the flow in the tank to slow down, even better.

One way of achieving the shut down is to have the pump on a timer. This is the quick and easy way, but the preferred method is a variable flow device (VFD) to slow down the pump to allow the skimmer to “simmer” so it can still function if there is a spawning event or call for skimming. A VFD also allows you to ramp up to wet skimming a few times a day to keep the skimmer neck clean, grab some stubborn semi-hydrophobic proteins and do a passive water change (just keep an eye on salinity).

Pumps with flow control are expensive. You may be able to set up a cheaper solenoid that restricts the air line feeding the needle wheel. You will have to get creative and rig it to shut only part way at night so some air can still bleed in. Drilling a hole in the solenoid may work, but I’m not sure how you will “tune” it. Skimmers with two or more needle wheel pumps make it easy because you just need to keep one pump on and put the rest of them to sleep at night.

At this point in time you are probably asking yourself, “Then why not just turn down the skimmer and run it 24/7?” or even, “Why not use an undersized or cheapo skimmer and put the money elsewhere in the system?” The key here is having skimmer reliability, and you simply won’t get that with the cheapo skimmers on the market. When they go “on strike” or flood the collection cup, when the air intake crystallizes, or the water level varies, or the pump disconnects, or stops entirely, you don’t have a skimmer, and you can’t predict when this will happen. With a well designed skimmer, you buy peace of mind and in the long run, you pay less because you buy just one skimmer. In other words, do it right the first time, and do it once. The other option of running a premium skimmer on a slow and steady, conservative setting is a “neither here nor there” solution. You end up with the worst of both worlds because the skimmer neck will slow down efficiency with skimmate (muck) build-up in the neck, which you will have to clean manually. It also doesn’t achieve our goal of leaving the tank “natural” during the nightly plankton swim.

Shutting ozone down at night is a parallel issue. You can put your ozonizer on the same timer as your needle wheel pump. Your ORP controller may have a day and night setting. UV sterilizers may be worth shutting down at night as well, but don’t start unplugging everything at once; ease into a night mode one device at a time over a few weeks. This way there is no shock to the system and you will have a better handle on the repercussions of each device.

While we are on the subject, there may be merit in shutting the refugium off during its night/dark phase. During the “day” algae utilizes/removes nutrients (nitrate, phosphate, heavy metals etc.) during photosynthesis (cellular respiration). The algae in your refugium converts “bad” CO2 into “good” O2; however, during the “night” (photorespiration) algae converts O2 into CO2 thus lowering the pH (liquid CO2 is carbonic acid, and like any acid it lowers pH). The same pH shift and gas exchange occurs within your corals carried out by symbiotic algae (zooxanthellae). Many people run their refugium on a reverse photo-period (refugium illuminated at night and kept dark during the day) to balance the pH and photosynthetic processes of the refugium and display. During the day, the zooxanthellae are generating O2 for the refugium while consuming the CO2 the refugium is producing, and the reverse process at night. At night the algae in the refugium leaks out some of its nutrient catch. If you take the refugium off-line during its night/dark phase, it assures that the leaked nutrients don’t make it to the display tank. When the lights come back on over the refugium (which should have 16 hrs of light and 8 hrs of darkness) the algae will re-absorb the lost nutrients.

[subsea]

I worked with Municipal Wastewater Treatment and had to go to conferences that talked about "the bugs that keep us clean". One research paper studied, envolved the stressing of bacteria with a resulting ten fold increase in phosphate uptake by the bacteria. In wastewater treatment, phosphate is the more difficult nutriant to remove. By cutting back on oxygen feed to diffusers in an activated sludge (detrius) plant, operating cost were reduced by 30% and phosphate uptake was accelerated.

The sceanario you outlined above cound easily describe what we did in waste water treatment 30 years ago.

Patrick

[+Grog]

I will be ordering some seaweed and refugium kits from http://live-plants.com/ shortly after Christmas. There selection of plants is limited during these winter months. If you are interested, I'll let you know something after I talk to Russ. The shipping is $14 flat rate.

Thanks for that link. They had a few items I hadn't seen elsewhere. And you are right, lots of stuff is unavailable right now.

[Bannerfish]

Thanks for that link, I definitely see some stuff I would love to have