The History of Pico Reef Biology

The 'tank' as of 24th February 2010

The idea for a truly long term micro/pico reef (for this article, one gallon or less) came to me as I was graduating college and searching the early internet forums for ideas on small reef aquaria in 2000-2001 to see what was possible and establish the current limitations of small marine aquaria. The smallest I could find, in the history of reef aquarium work altogether and in a lot of searching online, were 2.5 gallon tanks- some ranging back into the 1970’s (Thaler Puddle, Dr. Ellen Thaler for example) and an article on Reefs.org interviewing DC Potts about his successful pico tank from the late 90’s.

In 2001, even pictures of quickly-assembled gallon and half-gallon experimental aquariums (now common) were not available across the web, especially those using synthetic saltwater, so it was truly untested waters to work with half gallon aquaria that had to meet strict criteria to be valid in my opinion: they had to develop and sustain a diverse population of stony corals, benthic organisms and coralline algae, meet all water support needs with reasonable care (for example, no daily water changes) and they had to last-as long or longer than large aquaria without going eutrophic (high nutrient/algae dominated) relying on biology, not mechanical devices, to run the micro ecosystem. In hindsight they would break every rule the current establishment held against ultra micro aquaria, using simple science anyone could replicate, and the vast resources of the web had the friends I’d need to do it.

Lastly, they had to stand the test of master aquarists across the internet when reviewed-the technophiles like the guy at the rock concert who can tell when the guitarist messes up a single note. Emerging from all that scrutiny and time in preparation should be a new way keeping corals in the home…it’s still evolving as we all exchange ideas and new designs on blogs like this one.

The Reefbowl

One day when walking through Wal-Mart and thinking about design options, I noticed the curved 1.5 gallon vases for a few dollars and thought that would be a neat trial run, a seven dollar reef aquarium. When looking at the vase and thinking about substrates, pumps, etc it dawned on me the little plastic dishes I was using in the lab to keep pothos vines watered seemed the exact diameter of these large vases, maybe it would function like a lid if inverted? So I took the vase home, filled 1/3rd of it with oolitic substrate and saltwater and decided to bubble it instead of a pump, primarily I wanted to use gear I already had and the old aquarium pump happened to be there.

I knew not to add animals; this was just to test heating and salinity control. Well in four days the salinity had only increased from 1.023 to 1.024, the water line dropped only a quarter inch, and that was it-the design was lucky and worked perfectly with no further modifications. For the first time, a gallon reef aquarium had surpassed the top off requirements of a 100-gallon aquarium without complex equipment, and it was easily repeatable to anyone who wanted to try with common Wal-Mart supplies. The air stone met all the circulation requirements of the tank, it kept CO2 from accumulating so it lent strong pH support, it is the absolute ideal way to run a vase reef for these reasons, above any water pump. No animals in situ mind the air bubbles whatsoever… Normally, this combination of gear would be frowned upon in the established reef circles, so this presents another way to bend the rules unique to pico reefs.

The vase continued to evolve and it can be found by searching for anything with vase reef or reefbowl (non spaced) in the wording, there are thousands of threads about it all over the web because I spend a lot of time promoting, discussing and helping others replicate the art. My current vase reef is 4 years old and I expect it to run much longer barring hardware failures (knock on wood). Recently my friend Mark K. (Warlion) developed the vase even further by drilling the line access into the vase, rather than over the lip. This has added two more days between top offs, an unheard of maintenance schedule for any reef aquarium.

Additional pico reef photos can be found here.

The 1/2-gallon PalmTop Reef-No Evaporation

As the reefbowl sat and inspired me further, collecting simple corals that got along well, other ideas such as complete sealing came into mind and one day it snapped in my head to simply include a refugium as a rear subdivision in a tank, obscured by a false reef wall, to use photosynthesis to pump out oxygen under a sealed lid. This would bind respiratory waste CO2, stop evaporation altogether, it would bind up nitrogen and phosphates in the macro algae to some degree, and combined with weekly water changes (something not procrastinated if only one gallon and three minutes) the Palmtop Reef was assembled out of a special beta tank available at the time.

The first long term half gallon reef aquarium documented on the internet, and still the only fully documented sealed reef aquarium (non evaporating) of any size, this helped pico reef keepers find a unique niche among large-tank husbands who were once sure such a thing was impossible I could see in the web forums. Together online we worked out a carbonate dosing system for the micro tank which produced miniature acropora tabular growth and copious coralline algae, this indicated the ion support was spot-on even with no testing of any water parameters outside of salinity! My simplicity requirements had been met--no exceeded.

There was so much helpful input from other posters along the way to help me further my cause, Lunchbucket (Eric Peterson) is a fine example, he and I go way back in the reef forums (before 2003) and his tanks were a source of wonder for me as well along with many other board regulars who chimed in with support and help as needed …all the help needed was on the internet and for that I am so grateful.

Chemical/Physical Changes

Over the years in discussing forum threads about keeping marine aquaria in odd shaped containers, we are starting to see how shapes beyond the standard open square aquarium greatly change, and assist, the keeper if they are willing to make tradeoffs. The first tradeoff is fish, don’t use them in any pico reef is my best advice. I have experimented with fish like gobies before, and don’t agree they should be kept in ultra small aquariums.  By excluding fish in the design, there are no size restrictions for aquaria that can grow scleractinian corals.

For example, the fluted vase reef design is an absolutely critical shape for many reasons. The slant of the neck above the water line and under the lid forms a catch surface where the popping bubbles eject various fragments and wastes from the water column; this can be wiped periodically and is essentially a functioning skimmer. The lid rests on the inner diameter of the vase neck, something not possible in square tanks, and this directs the splatter back down into the bowl and away from the edges where salt creep would form in the usual situation around a lid, and it also seals the tank, taking it from a 2x daily top off opened to a twice weekly top off with a lid!

Continuing the ways container shapes change the physicality of a reef aquarium, Orb-type nano reef aquaria reveal an ever-increasing surface area for evaporation to occur as the water level drops (small surface area when full, large surface area approaching the equator of the orb or bowl) so the salinity increase is on an apparent log-scale just like pH, it’s not a consistent evaporation rate when compared to a square tank. Evaporation rates between days 3-4 are markedly faster than on days 1-2 on a globe/orb saltwater aquarium after a top off because as the water level drops more surface area is exposed to amplify water loss.

For total salinity control, small containers that can be sealed, and subdivided for plant growth, are the right size to use small lights and pumps that would otherwise overheat a larger sealed reef attempt and these small containers are also dwarfed by a basic desk fan when cooling needs arise during summer months. Knowing these variables ahead of time greatly hastens reef work in odd or small containers; this is helpful to keep in mind.

Just to mention a few final observations, which are better left as subject material for expert marine biologists, pico reefs are also changing what we observe as allelopathy or “war mechanisms” in scleractinian or “stony” corals because of the concentration ratios seen in these tiny tanks. How is it possible for 15 genera of coral, plus assorted invertebrates and mollusks, to share a gallon of water day after day in between servicing for years and not nettle the water into a mucus-laden soup?

These answers can be found in the further study of pico reef biology, there should be lots more to come over the new year as others make their observations known and we all continue to create a collective knowledge pool for the matter.

In closing, some people feel the micro reef designation will soon become the most popular in the hobby for a number of reasons listed in common nano reef articles (cost/footprint etc). A keeper or a future keeper of pico reef aquaria will have done much online research to get where they want to be since that is the only material available on the matter, so this networking combined with the use of maricultured corals and tempered experimentation should continue to bring our hobby into new homes at an astounding, and ethically sustainable rate.

If you have any questions or would like to discuss pico reef biology even further, be sure to leave a comment below.