Can Purple Non Sulfur Bacteria Replace Lanthanum Chloride? Data From ACI Aquaculture & Hydrospace LLC

Managing Phosphates in a Coral Wholesale Facility using Purple Non-Sulfur Bacteria (Rhodopseudomonas palustris) 

“PNS has been a huge Asset to the ACI Aquaculture soft coral receiving system.  Not only do the corals look healthier, but we have almost completely eliminated the use of Lanthanum chloride for PO4 control.” –Chris Meckley 

Phosphates play a nuanced role in the metabolism of all coral species. In photosynthetic corals, phosphates are essential in regulating the activity of Symbiodinium and other symbionts. In non-photosynthetic corals, obtaining phosphorus through living forage is essential to sustaining growth. Even in fish-only aquariums, unmitigated dissolved phosphate levels result in excess algae growth and can ruin tank aesthetics. Phosphates have both obvious and nuanced effects on the health, growth, and coloration of any given reef aquarium.

NPS in ACI’s soft coral flat.

The pressures of phosphate management increase proportionally with the scale of the aquatic system and the biomass of organisms being kept within it. Public Aquariums often struggle with phosphate management, as they must maintain brightly illuminated display systems, which are often densely packed with high-value specimens. The need to keep high densities of precious specimens well-fed is often at odds with the objective of reducing unsightly algae growth. Commercial fish and shrimp farms do not care about the aesthetics associated with high phosphate levels. However, they very well have a vested interest in mitigating the amount of phosphorus concentrated in their effluent water. Phosphates from both agricultural and municipal wastewater can rapidly destabilize wild ecosystems through eutrophication and harmful algae blooms. Phosphates are a necessary component of life, without which there would be no cell membranes and no ATP. But when excess amounts of phosphates exist in a system, biological diversity is destroyed rather than nurtured. Therefore, it is the cautious obligation of the aquarist, the aquaculturist, the farmer, the pool cleaner, the wastewater treatment plant operator, etc… to understand how phosphates affect the needs of their specific system, to recognize their limitations in being able to modulate phosphate in that system and to explore all efficacious avenues allowing for a greater degree of beneficial control. 

Amazeballs Goniopora.

Modulating phosphate levels in any aquatic ecosystem, let alone a reef aquarium, can prove to be a difficult and frustrating endeavor. The need to actively feed fish and satisfy the symbiosis of corals means that phosphates cannot be treated like a pathogen. They cannot be banished, quarantined, and ignored. They are the natural end result of healthy fish digesting their meals and are the necessary fuel driving coral-symbiont photosynthesis. Success, by every sentiment in reef keeping, implies phosphates are present in the system. Conversely, uncontrollably elevated phosphate levels are associated with a decline in stony coral health, stress to sensitive fish, and growth of nuisance algae. This tightrope of balancing phosphate levels towards some ‘goldy-locks’ zone of acceptability is the confounding task facing all reef aquarists. 

Balancing phosphate levels within any one given reef aquarium is a daunting enough task, but pursuing such balance on a commercial scale is a truly herculean feat. The Coral Wholesale Industry is the primary means by which non-tropical nations import marine ornamental livestock from wild reefs and commercial mariculture farms. On any given day or week, shipments from around the world arrive at such facilities. When these shipments arrive, they contain mass amounts of coral, all of which have had a long journey and all of which must be housed immediately. It is a delicate balancing act of time, labor and resources to ensure that the majority of imported animals do as well as possible. These wholesale coral systems must be filtration powerhouses in order to preserve stable water quality. This proves extra challenging in the wholesale setting when systems routinely receive shipments full of stressed and ailing colonies, all soaked in dirty travel water. To successfully operate a business such as this, requires the wisdom to accept that not all things are controllable as well as a ruthless willingness to understand what is. 

Chris and Amanda Meckley own and operate ACI Aquaculture, a coral wholesale facility in Plant City, Florida. Every hour of every day, they work to understand and control the phosphate levels in their many coral wholesale systems. Meckley’s business depends on its ability to retain, and sometimes recover, the health of the coral colonies that are received from across the globe. This objective comes with many complexities, such as pests, coral warfare, and coral nutrition. However, few challenges are as overarching as the need to efficiently and economically manage phosphate levels amongst ACI’s various coral wholesale systems. It is with this goal in mind that Chris and Amanda Meckley began working with Hydrospace LLC, testing their PNS Probio product out on a coral reef system much larger than that of the average hobbyist. The objective of the trial was to monitor phosphate levels in ACI’s Soft Coral Wholesale System while routinely dosing Probio over the course of 12 months. 

The Coral Wholesale System  

ACI’s Soft Coral Holding is a 1600-gallon system with two main holding fiberglass tanks and a sump containing 20+ year-old live rock. The system is powered by 2 Dolphin Ampmaster 6250 external pumps, two Octo plus four pumps, and 5 Sicce Voyager HP10s. The two main fiberglass tanks hold a variety of soft coral taxa (Sarcophyton, Xenia, Zoanthids, Clauvularia, Capnella, Sinularia) as well as some stony corals (Catalaphyllia, Cyphastrea, Goniopora). This system also houses a variety of non-photosynthetic coral (Euplexoria, Tubastrea, Dendrophyllia, Dendronepthea, Scleronepthea, Steronepthea, Carotalcyon, Menella, Acanthogorgia, Echinogorgia, Maricela, Guaiagorgia, Umbellulifera) and ornamental sponge (Clarhria, Helichondria, Tridentine) species. The system is illuminated by seven all-blue Reef Bright XXO LEDs for 12 hours a day as well as five 250-400 watt metal halide fixtures for 5.5 hours a day. The system has several dozen fish, including several large tang specimens (Acanthurus, Zebrasoma, Naso). The tank is fed three times a day with PE mysis pellets, frozen PE mysis, frozen Calanus copepods, frozen Artemia, and dried nori. The system has a protein skimmer and is equipped with two algae scrubbers. The system receives 200-gallon water changes weekly and is dosed with lanthanum chloride when phosphate levels exceed one ppm. Before the trial began, lanthanum was dosed into this system once or twice a week.   

NPS gorgonian’s happy with polyp extension.

This coral wholesale system expects monthly shipments of 300+ pieces of coral, many of which are shipped in wild water full of organics. This means that even healthy shipments are essentially phosphate bombs that threaten any previously established balance in the system. Despite all of the photosynthetic activity from corals and algae scrubbers, phosphate levels in this system spike sharply after incoming shipments and need to be continuously mitigated by one of two methods. This is water changes and dosing of lanthanum chloride. It is well understood that water changes generally have overarching benefits to most coral systems, but at a commercial scale, they can be economically prohibitive. Too much overturn in such a system could also deplete levels of bacterioplankton, zooplankton, and other forage needed by non-photosynthetic corals. Lanthanum chloride is a tempting alternative, as it lowers dissolved phosphate levels without a water change. However, this particular compound is a known toxin to many fish and invertebrate species. Certain fish, such as tangs, show special sensitivity to this chemical. With this in consideration, it becomes apparent that the three primary means of reducing dissolved phosphate in the system (photosynthesis, water changes, lanthanum) all have their merits and their limitations. Dosing phosphate-consuming bacteria presents itself as a complementary solution to modulating phosphate levels in this complex holding system.        

The Bacteria (Rhodopseudomonas palustris) 

Rhodopseudomonas palustris is a purple non-sulfur bacteria that is gaining popularity as an alternative means of phosphate management. Due to its swiss-army knife metabolism, Rhodopseumdomnas can conduct a wide variety of ‘biofiltration’ services. Within the context of phosphate mitigation, R. palustris’ ability to photosynthesize is of great value. Photosynthesis is undoubtedly a significant factor in the phosphorus cycling of any aquarium. However, most attention is paid to catering to aerobic photosynthesis as it occurs within the tissues of corals, the algae scrubber, and the shallow surface of live rock. R. palustris is able to photosynthesize in anaerobic zones and areas with minimal oxygen. Having such bacteria present increases the number of microhabitats where photosynthesis can occur and how much localized phosphates can be consumed. Even in the dark, R. palustris is also able to consume phosphates via heterotrophy. This is the ability of a microbe to use oxygen to ‘eat’ organic matter. Excess phosphates continuously leach from built-up organics in the water and on/between surfaces. If organics are consumed by bacteria cells, then the phosphates they contain remain trapped in that cell, enveloped in a package that can either be removed by the protein skimmer or reclaimed by a feeding coral. 

ACI’s bulk PNSB Pro Bio.

Rhodopseudomonas palustris is the growing subject of experimentation within the realm of wastewater management. Kim et al 2004 reported that R. palustris cultured in swine wastewater dropped dissolved phosphate levels from 180ppm to 80ppm after seven days. R. palustris is an attractive alternative to chemical treatments, such as lanthanum, because it reduces dissolved phosphate levels without inducing stress on fish and other livestock. This bacteria species has been associated with a variety of mangrove, fish, shrimp, sponge, and coral species and likely plays a role in regulating phosphates in wild reefs. Although extremely promising, the capacity of R. palustris to be purposefully deployed and regulate phosphates in established coral aquaculture systems is a subject that has yet to be crystallized and will be actively explored over the coming years. This trial is an early attempt to measure the practical benefit this probiotic offers to the maintenance of a heavily stocked coral wholesale system.  

The Trial

Five-gallon cubes of live R. palustris culture (Probio) were provided by Hydrospace LLC to ACI Aquaculture throughout the course of this trial.  The trial was conducted from April 2024 through November 2024. Water testing was conducted every other day with iDip PO4 test strips as well as a Milwaukee PO4 Photometer unit. 650ml of Probio was dosed into the system five days a week. After August 7th, 2024, the dosage was increased to 800 ml. Lanthanum chloride was dosed into the system whenever phosphate levels exceeded 1.2 ppm.     

Sohal tang in the soft coral system at ACI.

Results of PNS Probio Dosing Trial 

It must be plainly accepted that the data provided by this trial must be observed through the chaotic context of an actively operational coral wholesale system. Throughout the course of this trail, individual corals were being removed and introduced as animals were bought and sold. With this in mind, there is little in terms of scientific consistency that can be accepted from this data set. What can be accepted is the overall ‘story’ depicted by the phosphate levels over these months. The above figure is defined by spikes and valleys in phosphate concentration. The ‘spikes’ (over 1ppm) in phosphate concentration can be attributed to a series of known factors (animal waste, animal die-off,  feeding, etc.). Chris and Amanda Meckley’s experience has confirmed that 200-gallon water changes occurring every two weeks combined with the system’s normal photosynthetic load (corals, scrubbers, etc.) are not enough to keep phosphates below detrimental levels. The resulting action is the dosing of lanthanum chloride, which is responsible for the dramatic drops of phosphate concentration towards zero ppm. It is the dramatic and immediate nature of these phosphate drops that is concerning to the Meckleys. Such abrupt fluxes in nutrient availability overnight go against the overall stability they desire. Furthermore, each dosing of lanthanum chloride delivers observable stress to the system’s precious tang specimens. The intervals in between this ‘bottoming out’ of phosphates and the next peak towards 1ppm is the general ‘goldy-locks’ zone desired. These are the time periods where phosphates either stay relatively constant or exhibit a slow, gradual ascent toward undesirable levels. Elongating and perpetuating this time of gradual phosphate stability is the main benefit ACI attributes to dosing PNS into their system.         

“If I add 200 more mls of PNS, then I’m adding less lanthanum. With the PNS, I’m adding lanthanum every  5 weeks versus every 3 to 4 weeks.“–Chris Meckley  

Conclusions 

Chris Meckley has found PNS Probio to be an attractive addition to his tool belt of phosphate management. Unlike water changes, PNS Probio can be deployed with minimal labor and has been demonstrated to lower measurable phosphate levels at a much more gradual rate than lanthanum chloride. Unlike lanthanum chloride, Rhodopseudomonas palustris has not been demonstrated to be a toxin to various fish and invertebrate species. On the contrary, R. palustris is a naturally occurring probiotic that has been associated with growth promotion in a myriad of animal and plant species. Another exciting consideration is the fact that various filter-feeding sponge and coral species are capable of grazing on R. palustris. This means that not only does this method of phosphate reduction not directly harm the aquarium’s occupants, but it also provides a means for phosphates to be gradually converted into nutritious microbial proteins, lipids, and pigments. It is this conversion of waste phosphates into bacteria live feed that Chris Meckley finds encouraging enough to continue doing this probiotic into his system.

Though promising, this early trial only scratches the surface of formally evaluating the ability of dosing Rhodopseudomonas palustris as a mechanism of phosphate modulation in coral reef aquariums. Obviously, an active coral wholesale system is not the ideal test subject for formal scientific evaluation, and there are several apparent avenues for translating these promising observations into a more controlled setting. Attempting to produce replicant systems with a limited and uniform set of coral/fish/inverts would be an ideal follow-up experiment. One in which half the systems did not receive PNS dosing and the other half did at regular intervals and if phosphate levels were measured for a period of a year or more. This would be helpful in confronting the natural follow-up questions cultivated throughout the course of this trial:

Would increased PNS dosage result in proportionally reduced phosphate levels?

How long was the PNS persisting in the various microhabitats of the system? 

Could certain environmental factors (lighting, salinity, nitrate levels, substrate, etc.) increase or decrease the efficacy of PNS dosing? 

What proportion of the PNS biomass was consumed by corals and other filter-feeders vs collected by the skimmer or removed through water changes? 

High end long tentacle anemone at ACI Aquaculture.

It should also be stated that strictly experimental setups are costly to build and laborious to maintain and potentially end up not reflecting commercial conditions. In all likelihood, eight ‘identical’ reef tanks could develop extremely variable fluxes in phosphates, making the production of true controls extremely challenging. Oftentimes, by seeking more consistency, the truth becomes ever more cloudy. With that in mind, the value of more informal trials such as the one described cannot be entirely brushed aside. It is within the commercial realm, not the laboratory, that technologies prove their true worth. The application of live probiotics is a technology still in its infancy at large, let alone within the specific realm of reef aquarium keeping. However, the short- and long-term benefits of this early trial are apparent enough to be celebrated. It would be of extreme benefit to public aquarium keepers to have a means of controlling phosphates and nuisance algae in their displays without risking poisoning precious specimens with lanthanum. It would be of even grander benefit to have phosphates stripped from agricultural/municipal wastewater before it could destabilize wild estuaries, rivers, and reefs. Rather than being an environmental poison, phosphorus could be strategically reclaimed into microbial nutrition that is fit to feed shrimp and coral alike. Despite limitations of control, this trial offers many promising avenues of exploration pertaining to the application of Rhodopseudomonas palustris in phosphate management. The fruits of such explorations will likely benefit many future reef aquariums massive and small. 

A Note From The Editor

This type of effort is paramount and extremely welcome in the industry. Much of what we have spoken about at Reef Builders over the last six months has been an attempt to encourage companies to champion their products by asking and beginning to answer the hard questions. Hydrospace LLC, ACI Aquaculture, and Taras teamed up to do just that. This pilot study should be celebrated as an enormous step in the right direction regarding the industry’s transparency and R&D. Hopefully, we can see more specific experiments like this one as time passes. Funded by companies but for the people. All in all – this sets a new and welcome bar for manufacturers and begins to answer the question, “What happens when I add this to my tank?” This is one small step for science – one giant leap for the industry.

– Salem Clemens

Literature Consulted 

Barry, M. J., & Meehan, B. J. (2000). The acute and chronic toxicity of lanthanum to Daphnia carinata. Chemosphere, 41(10), 1669-1674.

Behets, G. J., Mubiana, K. V., Lamberts, L., Finsterle, K., Traill, N., Blust, R., & d’Haese, P. C. (2020). Use of lanthanum for water treatment A matter of concern?. Chemosphere, 239, 124780.

Chu, T. W., Chu, Y., Sun, W. T., Pan, C. Y., Pan, C. H., & Ding, D. S. (2024). Nutrient enrichment and probiotics for sea urchin Anthocidaris crassipina larvae in captivity to promote large?scale aquaculture. Journal of Animal Physiology and Animal Nutrition.

Getha, K., Vikineswary, S., & Chong, V. C. (1998). Isolation and growth of the phototrophic bacterium Rhodopseudomonas palustris strain B1 in sago-starch-processing wastewater. World Journal of Microbiology and Biotechnology, 14, 505-511.

d’Haese, P. C., Douglas, G., Verhulst, A., Neven, E., Behets, G. J., Vervaet, B. A., … & Spears, B. (2019). Human health risk associated with the management of phosphorus in freshwaters using lanthanum and aluminium. Chemosphere, 220, 286-299.

He, Q., Zhao, H., Teng, Z., Wang, Y., Li, M., & Hoffmann, M. R. (2022). Phosphate removal and recovery by lanthanum-based adsorbents: A review for current advances. Chemosphere, 303, 134987.

Hua, D., Wang, J., Yu, D., & Liu, J. (2017). Lanthanum exerts acute toxicity and histopathological changes in gill and liver tissue of rare minnow (Gobiocypris rarus). Ecotoxicology, 26, 1207-1215.

Huang, K., Lai, S., Guo, M., Zhu, X., Yuan, J., Liu, Z., … & Gao, Y. (2024). Comparison of toxicity between lanthanum oxide nanoparticles and lanthanum chloride. Journal of Rare Earths, 42(2), 424-430.

Kim, J. K., & Lee, B. K. (2000). Mass production of Rhodopseudomonas palustris as diet for aquaculture. Aquacultural engineering, 23(4), 281-293.

Kim, M. K., Choi, K. M., Yin, C. R., Lee, K. Y., Im, W. T., Lim, J. H., & Lee, S. T. (2004). Odorous swine wastewater treatment by purple non-sulfur bacteria, Rhodopseudomonas palustris, isolated from eutrophicated ponds. Biotechnology letters, 26, 819-822.

Kriek, C. G. (2022). The design and operation of a membrane photobioreactor using Rhodopseudomonas palustris for simultaneous wastewater treatment and biohydrogen production (Doctoral dissertation, Stellenbosch: Stellenbosch University).

Krol, L., Melton, B., Delbeek, J. C., Dunker, F. H., & Shepherd, B. (2023). The Iconic Philippine Coral Reef at Steinhart Aquarium: The Husbandry, Welfare, Behavior, and Veterinary Care Considerations of a Large Multi-Taxa Living Coral Reef System. Journal of Zoological and Botanical Gardens, 4(4), 738-750.

Larimer, F. W., Chain, P., Hauser, L., Lamerdin, J., Malfatti, S., Do, L., … & Harwood, C. S. (2004). Complete genome sequence of the metabolically versatile photosynthetic bacterium Rhodopseudomonas palustris. Nature biotechnology, 22(1), 55-61.

Raina, J. B., Tapiolas, D., Motti, C. A., Foret, S., Seemann, T., Tebben, J., … & Bourne, D. G. (2016). Isolation of an antimicrobial compound produced by bacteria associated with reef-building corals. PeerJ, 4, e2275.

Selvin, J. (2012). Process optimization for the production of antimicrobial compounds from marine sponge associated bacteria Rhodopseudomonas palustris MSB 55. Indian J. Innovations Dev, 1(2).

Zhang, Y., Yang, Q., Ling, J., Van Nostrand, J. D., Shi, Z., Zhou, J., & Dong, J. (2016). The shifts of diazotrophic communities in spring and summer associated with coral Galaxea astreata, Pavona decussata, and Porites lutea. Frontiers in Microbiology, 7, 1870.

Zhao, Y., Liang, J., Meng, H., Yin, Y., Zhen, H., Zheng, X., … & Zhang, K. (2020). Rare earth elements lanthanum and praseodymium adversely affect neural and cardiovascular development in zebrafish (Danio rerio). Environmental Science & Technology, 55(2), 1155-1166.