Nano Bubbles in the Reef Aquarium

As Don Ho used to sing:” Tiny bubbles, in the wine, make me happy, make me feel fine”. However, this refrain does not seem to be the mood on the reef aquarium side of the hobby, as judging from the heated discussions and flaming that has been going on in regards to the ‘technique’.

Depending on who you ask, adding nanobubbles to one’s tank is the best thing possible and a large jump in reefkeeping methodology, or it is simply another sign that the Apocalypse is upon us. Having seen everything from trickle filters to the Aqua Ecolizer, a magnet that you ran your water through to help it cleanse more thoroughly, as well as countless additives and potions that did more harm than good, my feeling is that doing this is probably somewhere in between these schools of thought.

So what exactly does adding nanobubbles mean? What are they supposed to do? Most importantly, what evidence have we seen to even consider their use? ‘Nano bubbles’ are not what we typically see when we see bubbles in our tanks – they are incredibly small at only 1-50 microns in diameter. Due to this small size they do not all float to the top like typical bubbles do, but instead stay within the water column before dissolving.

Because of their small size and non-floating behavior, minimal buoyancy, they are more difficult to see than normal bubbles and are usually easiest to see at night or in sunlight when light reflects off the bubbles. So because they float through the tank for an extended period of time, in theory they make the entire tank act like a giant protein skimmer.

Proteins and other harmful compounds adhere to the bubbles and eventually float to the surface where they can be skimmed out. Nanobubbles have a minimal buoyancy and a net negative charge which helps the nanobubbles to adhere to detritus particles. In theory, a nanobubble with an upward buoyancy force of .001 Newtons would require 1,000 of them to attach to a detritus particle to become more buoyant than water.

Since the use of these bubbles should be administered over hours, eventually the bubbles should, in theory, find their way into the nooks and crannies of the tank, rockwork, and even sand bed, where detritus settles, and help reduce its level. These bubbles are also purported to enhance the health of corals by causing them to excrete more mucous which helps to remove waste and pathogens more readily than when not enough mucous is produced.

This application of nanobubbles in a reef aquarium seems to also be more of a nutrient transport mechanism that carries out and floats out detritus and other pests out of the display tank, and into our export area; the sump. ? Coral mucous consists of excess polysaccharides and a study done at Heron Island, Australia shows how mucous shedding and floating is part of the nutrient export and cycle of a typical coral reef without detriment to the health of the organisms. So, mucus shedding, floating and export from the system can create a lower nutrient system by effects of removing the excess nutrients and or detritus or food particulates in the system efficiently.(http://www.nature.com/nature/journal/v428/n6978/fig_tab/nature02344_F3.html)

Julian Hechavarria and Cruz Arias (of Elegant Corals, LLC), and Tullio Dellaquila have all been experimenting with this  idea for more than a decade, so this is not something new, though the application and delivery method is cutting edge. However, from what I have seen and read to date, there is little scientific study to show the benefits of nanobubbles use in reef tanks. However, having done this for a while, it is my opinion that if we had waited for double blind peer reviewed studies to come out proving that what we were doing worked, we would all still probably be using trickle filters.

So this raises the question of where did this come from and why did some reefers try it? From what I understand, the use of nanobubbles was first used and documented in Japan, where the introduction of nanobubbles to Kusuura Bay between 2003-2007 helped to revitalize the bay and caused fish to grow much faster. From this experiment several papers were published hypothesizing about the benefits of nanobubbles and this is what got things started on the scientific side [Ed. Note: the benefit could easily be due to simply increasing dissolved oxygen content].

For the hobby, the use of the limewood airstone near the return pump was discovered by accident when Cruz left the limewood diffuser running in the return chamber of his sump in the early 2000’s, before leaving for a few weeks of vacation. When he came back, he noticed that there was significant growth in his corals and a visible change in water clarity after he shut off the air pump. He was expecting to come back to a dead tank.

In addition to the benefits described above, according to proponents of their use, nanobubbles have the potential to not only do the obvious and improve oxygenation, but also kill off algae and cyanobacteria by removing detritus, diminishing or decreasing coral diseases by improving/increasing coral mucous production, and improving overall water stability. The improved oxygen content may also improve the health and vigor of fish as shown by their increased swimming, grazing and maintaining improved coloration.

The use of these bubbles may also improve coral health by keeping the pH more stable and making the water clearer, which allows more light to penetrate, and it’s surely having a benefit on dissolved oxygen concentration. Opponents of this methodology insist that it will do little to an already healthy tank and that the increase in bubbles may irritate the corals and fish leading to greater risk of disease, cause salt creep and just add more useless and costly technology to a tank.

So after reading several of the threads on this and talking with some of the proponents and opponents, I decided to try it out to see what if any difference it made on my tank. To be honest I did not expect a whole lot on my or any other tank, as at this point I think for the most part we are all pretty successful so at best what I expected would be an incremental improvement in my tanks.

I also thought this might be of some benefit, since I like most of us, really has no idea what the dissolved oxygen level is in any of my tanks. I also thought that once the lights went out that it probably did fall since my tank is so packed with photosynethetic corals that oxygen content had to fall while CO2 had to rise when the lights are off. Also since my tank like most is full of lots of nooks and crannies that are anoxic or anaerobic, this might help bring oxygen to those “dead spots” as well and be beneficial in doing so.

So at first, I started slow with a homemade “nanobubbler” which consisted of an airstone under a powerhead with a funnel attached to draw in all the air produced as well as enough water to distribute the bubbles. And at first I ran it for two hours a night for the first week. Since I work in the field of medicine, the first thing I wanted to see was that it did no harm.

During that time, the corals, where the bubbles flowed, did produce extra mucous, but other than that there was nothing exceptional, that I saw. So thinking a small amount was okay, I decided to increase the time to 8 hours per night. I chose to run the unit at night as the bubbles were not pleasing to see in the tank and the general consensus was that using nanobubbles at night would be the best way to keep the tank stable.

After doing this the first night there was indeed a significant amount of mucous to be seen sloughing off the corals when the lights came on and the unit shut off. But I was not alarmed as this is what was supposed to happen. Unfortunately, after a few nights it was apparent that something was wrong, as a couple of corals, or rather parts of the corals, that were in the path of the bubbles, bleached out and died.

I quickly determined, that in my zeal to build this unit, I did not take into account that the way it was assembled, the contraption produced significantly more large type bubbles than the desirable nanobubbles, and as a result, these large bubbles did indeed irritate the corals to the point that they suffered.
So I then undertook further reading and redesigned how the nanobubbles would be delivered. Now an air pump attached to a limewood airstone was placed in the sump, where the return pump drew water from the sump.

By placing the airstone there, larger bubbles moved up to the surface and popped harmlessly, while smaller micro-nano sized bubbles were drawn into the return pump and where cavitation would break them down into the desired nanobubble size as well as the combined head pressure from the return piping. This system was turned on as the lights went out every evening and then off an hour before the lights came back on. This nanobubbler has now been in operation for almost 4 months and the results have been interesting and a bit surprising.

As with the first system, the primary goal was for this to do no harm and fortunately this has been the case. There has been no bleaching of the corals or bubble eye or swim bladder maladies in the fish. And as I expected, the results/improvements in the tank have been incremental in nature. For the first week or so there was more mucous from the corals in the morning, but this has for the most part subsided with time.

It should be noted that when this system is used, good water movement should be employed, especially when the lights come on in order to move this mucous off of the corals. If water movement is not adequate there is the potential for the extra mucous to foul the corals secreting it as well as nearby coral neighbors.

As an aside, another interesting aspect and potential for using nanobubbles is that they may also lessen the risk for corals to be infected by the bacterium, Vibrio corallilyticus, one of the potential pathogens purported in coral bleaching and RTN. In a 2013 paper by Denise Brehm, she found that stressed corals excreted a substance called DMSP in their mucous, and that this substance was a signal for this pathogen to attack.

Thus by having corals shed more mucous, theoretically it could cause them to also shed this substance and keep them from being infected by this pathogen. Again this is a hypothesis, but it does provide yet another possible avenue for investigation. Also since RTN seems to occur in our tanks more frequently during the hotter months of summer, it would be interesting to see if tanks employing nanobubbles do not or do experience any RTN or do so to a lesser degree.

I should note that the following results are from my well established, 300-gallon sps tank where I did not change anything else other than adding the nanobubbles to the tank during this time. While initially there was seemingly little change in the tank’s parameters, over time, these have changed slightly more. Over time, the pH has gradually shifted upwards possibly due to the alkalinity stabilizing.

Prior to the addition of the nanobubbles, the pH would drift down to 7.92-7.95 at night, whereas now, it only drifts down to 8.1 or so, which is a significantly smaller fluctuation. This is, no doubt, due to the bubbles simply driving off CO2 at night, by means of positive osmotic gas dissolution of higher O2 air into the water column, which is reducing the pH drop due to the large photosynthetic bioload that is in my tank.

In theory, the more stable pH, may lead to faster growth as maintaining a pH above 8.0 purportedly increases the rate of calcification. In this regard I have seen two corals, that had shown little growth for the six months prior to the introduction of nanobubbling, start to sprout and bud. However, this is purely anecdotal and I have seen other corals in my tank do nothing for long periods before suddenly showing unexplained growth, so I am hesitant to promote cause and effect at this time.

Similarly, my friend Ben Vandernoort, has told me that since he started using this technology and methodology, he now sees his frags, and he does a lot of fragging, start to encrust at 2 weeks, where prior to this it took at least a month. Ben keeps a beautiful well-maintained tank so again this may simply be the result of it now being in a sweet spot that is causing this, but it is another thing that can be easily tested for in the future. Ben also suggests that you can stabilize the pH even more if the air to produce the nanobubbles is drawn from the outside as shown in the accompanying picture as he does. As mentioned he believes this more stable pH that he is seeing is what may be leading to the faster encrusting by the frags.

In similar fashion the redox potential in my tank, has increased over 20 points since nanobubbling was started. This is similar to what was seen when an oxygen reactor employing ozone was used on the tank in the past. Redox potential for lack of a better term, is a reasonable measure of the “cleanliness” of the tank. It being higher, basically means that the water is slightly cleaner as a result of the use of the nanobubbles, in my opinion.

This phenomenon also may be why some hobbyists who are employing this technology report that in the morning their tanks have the “clean ocean smell” that is pleasant, rather than the sulfurous one that some tanks seem to have when the lights come on. Some also report that their water looks clearer in a manner akin to when they add new carbon or run ozone due to an age old practice of floatation clarification of particulates in the water column similar to what they utilize in wastewater, water treatment facilities around the world.

In more subjective terms, when a water change is being done on my tank, there appears to be less detritus being removed, while the skimmer seems to be removing about 20-25% more skimmate, each week. All of which may be a function of detritus adhering to the nanobubbles and being more readily skimmed off. But again this may simply be due to the tank currently being in a sweet spot. But that means that a lot of coincidences are occurring at the same time.

All of this is well and good, but it really is not anything miraculous. In terms of the corals and fish, they all seem as healthy, colorful and robust as before, but as with watching your kids grow up, it really is difficult for me to confirm if the growth has changed significantly, since for the most part I felt the growth was pretty good in the corals to begin with.

And the fish all seem to be eating with the same gusto as before and have maintained their colors. However, there has been one noticeable change. Before using the nanobubbles it was necessary to clean the front glass on the tank every 2-3 days. Now after 3 months of using nanobubbles, the glass now only needs to be cleaned once a week.

This may not seem like a big deal, but like most of us, I hate cleaning the glass as invariably I hit a coral or knock something over or when I don’t do it something falls into something else and I miss it, so to me it really is a nice benefit of doing this that I did not expect. And since all it really cost was a pump that I already had and an airstone it is worthwhile enough that I will continue to use it and document the long term benefits or if any problems arise.

As I said, when I added nanobubbles to my tank, I did not really expect more than an incremental benefit at best. And for the most part I have seen incremental improvements in terms of improved pH stability, stimulated coral growth, cleaner water and little additional cost or maintenance. Hopefully, after keeping tanks for a while now, I have “perfected” my methodology enough that anything I do really won’t change things that dramatically.

But, on a new tank or on a tank that is having some problems or is not quite where you want it, it is my opinion that trying nanobubbles might be worthwhile. And for anyone with an extra air pump and limewood airstone lying around, it is something that might produce an incremental benefit without a big cost. However, there are still a lot of questions that need to be answered such as what is the optimal run time and when, how long does it take to see effects, what are the long term effects, and is one methodology superior to another just to name a few.

As with many of the things we have tried in this hobby, it is only through trial and error that we will learn and perfect what we are doing, so in this regard I hope those of you who try this will document what you see, both good and bad. Hopefully this is another incremental step in our achieving the level of success we all desire.

On a closing note, I am not telling anyone to do or not do this or anything else. I am merely reporting on what I have seen for myself and what I have heard from other hobbyists. I hope this article encourages the debate and the continued experimentation in our hobby, that has gotten us to where we are today.