Nitrates 101: Dealing with them in YOUR Saltwater Tank!

Hi, Dross Pleskin here and welcome back to the Calypso Aquaculture Laboratory. And today we're going to be continuing our series mastering microbes and continuing our little subseries in that the nitrogen cycle. Kind of discussing the nitrogen cycle, why it's relevant in every reef aquarium, every planted aquarium, every fish only aquarium, freshwater, saltwater brackish. Nitrogen cycle is key. It's paramount. And today we'll be advancing our understanding past basic bofiltration, past nitrification. We'll be entering into a new level of nuance. Now the tank you see behind me is my little tank of misfit toys. All the fish from our various service clients that are a little roughed up and they can't quite find a new home somewhere else. They come live here with me. And uh we'll be using them today to recap our last episode. To summarize nitrification as a whole, we can kind of equivalent it to the Pac-Man effect where the fish is eating and then pooping. Ammonia is produced. We have a set of ammonia oxidizing bacteria. Nitroamonus in their kin consuming it secreting nitrite NO2 far less toxic. And then we have a second set nitroacttor in their kin. the nitrite oxidizers. That's consuming that nitrite into the far less toxic nitrate, the NO3. Now, that end process inevitably ends with one thing, rising levels of nitrate in the aquarium. Now, nitrate is far less toxic than ammonia and nitrate. That does not mean that we can allow it to build up inconsequentially to massive levels. Now, nitrate specifically in the reef aquarium causes many issues when it hits levels exceeding what the system can efficiently process. Once we hit higher levels exceeding 20, 30, kind of depends on the the context of the specific reef, but once we hit that double and certainly the triple digits of nitrate, the first thing that we start seeing is pest algae growth. Depending on how much light is available in the aquarium, you will have lots of other forms of photosynthetic life that utilize that excess nutrient that nitrate that you might not necessarily want for your clean aquarium. That's kind of the most benign consequence. Then as nitrate levels rise and rise, things that were very important in sustaining such as the intimate relationship between photosynthetic corals and the zoenthia that give them their health and their beautiful coloration. This relationship depends on the coral essentially living in a little bit of an igotropic or nutrient poor environment. We have lots of nitrates and uninhibited rise and unmodulated levels of nitrates rising. This partnership gets threatened and that's when we see corals lose their zoenthali lose their health and overall lose their coloration and their ability to grow if not survive. In our last episode about nitrifying bacteria, we observed how a redux reaction was undertaken by nitroamonus and nitrobactor and similar bacteria to oxidize or remove electrons from ammonia and nitrite respectively converting it into nitrite and nitrate. Ditrification operates in a reverse redux reaction. It's a reduction reaction versus an oxidation reaction. A fancy way of saying as opposed to taking electrons away, it is actually adding electrons to the nitrate molecule, converting it into N2 gas and water as a byproduct. This is a magical multi-step reaction generally summarized by the equation presented here. The caveat to this reaction is that it is one that cannot be successfully undergone in the presence of excess oxygen. In contrast to our conventional BOF filter bacteria which absolutely need oxygen in order to convert ammonia and nitrite, these bacteria, the dnitrifiers require an environment that is relatively oxygen poor. This is a magical process, one that takes that inevitable end waste product, the nitrate, and turns it into d nitrogen gas. Gas which inevitably bubbles up from the aquarium and just enters the air surrounding us. Nitrogen gas, which is potentially one of the most harmless components and molecules available to all forms of life. I just breathed in a bunch of it and it's absolutely harmless. So by having this molecular mechanism, these special bacteria have given us insight in how we can purposely remove nitrate all together from the aquatic ecosystem that we've constructed. So where on God's green earth are these denitrifying bacteria if they cannot be exposed to oxygen? The answer to that is both intuitive and counterintuitive. It's intuitive in many ways, as in one would simply need to think about where to look to find the minimal areas of oxygen inside our reef aquarium. The first place to go to is the bottom of a deep sand bed, if you have one. Past those first few inches, you have so much activity going on in so little interface with water movement that oxygen levels truly do get depleted in those lower sediments, allowing for denitrifying bacteria to set up shop. A similar set of environments can be found in the inner pores and inner spaces of live rock where again oxygen levels become so depleted that anorobic populations of bacteria can set up shop and be able to convert nitrate in these locations. Now let's say we have the aquarium behind me. It doesn't have a sandbed. Uh there is some live rock for sure, but there's also definitely dnitrification happening in other places in this aquarium as well, counterintuitively. Now, we've we've thought of some intuitive ways in the inner spaces of live rock and potentially in a deep sand bed, but there are also other small microhabitats that are relatively devoid of oxygen. These include some of the inner spaces of the guts in the intestines of our fish and our invertebrates. These are areas where you have lots of different microbes that are consuming oxygen and they can be synergistically metabolizing with anorobic bacteria providing them you know an area where oxygen is being stripped away but also an area where nitrate is abundant so that this activity can be going down. Another area and set of microhabitats where this could be occurring is inside the inner spaces in inner structures of the coral of the living coral skeleton itself where multiple different wild colonies of corals have been shown to have populations of species such as purple non-sulfur bacteria which are known denitrifying agents actively operating in an anorobic way inside the coral skeleton. So with this in mind, there are two major ways to establish these kind of habitats where one, we have ways where the oxygen is naturally depleted due to the actual structure of in the limited area of the crevices where we're at and then also this biological synergy where we have areas where other microbes are consuming oxygen at such a rapid pace that denitrification can occur. How do we get denitrifying bacteria in the first place? Well, the first way is the major form of pilgrimage for any aquarium, new or old. It is the live rock that one is initially putting in there either from an established old aquarium from the wild or intentionally through something like our TSA biomedia. Something that has been exposed to a coral reef aquarium or ecosystem that has the potential to have a little bit of this fully functional matrix intact and therefore is far more likely to have a set of organisms that are capable of denitrifying activity. The second major set is many companies are now leading the charge in actively culturing bacteria that have known capacities to dnitrify under saltwater reef aquarium conditions. This is where microbes such as the purple non-sulfur bacteria rotoamonus polustrus are extremely interesting in their potential to conduct denitrification even in the presence of oxygen because of again they're able to facively move their metabolism around so they can denitrify even if a little bit of oxygen is present. Ditrifying bacteria however are not a magical cure all for all woes in the aquarium. should be very important to acknowledge the limitations that we currently have both with our understanding and our ability to purposely deploy denitrifying bacteria and harness their metabolic potential. The first is scale. Because we are dealing with a limited amount of space and water, we cannot enjoy the same level of biopiltration scale these organisms have evolved to experience in the wild. One cannot dedicate 200 gallons of denitrifying surface area for every one gallon of water that is being dedicated to housing fish. And very often in our aquariums, we want to really push that that that carrying capacity, that bile load, the amount of fish, corals, all the fun, beautiful stuff we want well beyond what might be able to be passively processed by just bacteria alone without denoting some sort of monstrously sized scale uh denitrifying chamber. However, we do know that by purposely adding bacteria that we know can denitrify and encouraging their growth through areas of limited oxygen, also lots of live rock, and then potentially adding illumination to these areas, we know that we can at least encourage their levels of growth. But again, these are not an alternative to water changes in two ways. One, again, because of that scale, it's very unlikely that you'll be able to denote enough denitrifying surface area to compensate for large amounts of fish growing over time. But also, water changes provide the essential building blocks that these denitrifying bacteria need in the first place in order to conduct their metabolic wonders. They need all these enzymes, these special materials and components that they make in order to convert nitrate into N2 gas in the first place. These enzymes are made up of important trace metals and elements. Zinc, copper, malabidium, manganesees and the like. All these things that slowly become attenuated over time in the water column need to be replenished with you you guessed it water changes. So denitrifiring bacteria are not an alternative to water changes but are a potential to maximize the effectiveness of water changes. and water changes are absolutely essential in being able to maximize, accelerate, and sustain denitrifying bacteria that you're able to sustain already in your aquarium. Outside of the reef aquarium industry, denitrifying bacteria can be everything as far as bringing the awareness, the passion and love that the average reef aquarist has for its the beautiful animals that they try and take care of in their tanks and translating that into how we can take care of wild coastal ecosystems and wild oceanic ecosystems. Every reef aquarist knows that you cannot just let your nutrients rise and rise and rise and rise and rise and rise just like that. that we cannot be just releasing excess nutrients into wild water bodies by embracing dnitrifying bacteria. By having more people become inspired, make homemade reactors, play with modulating their own nitrate levels, all within the lens and context of passion of keeping something beautiful alive. We may very well discover the keys, tricks, and insights required for those beautiful next generation reactors that will strip nutrients and nitrates out of our wastewater and allow for the effluent of humanity to benefit and increase the growth of the surrounding wild ecosystems versus inspiring neutropy uh all kinds of pest algae growths and eventual organic overload and collapse. So in conclusion, dnitrifying bacteria give us a potential means of a set of organisms that can actually consume that end nitrogenous waste compound that nitrate and actually convert it into N2 gas and have it escape our aquatic ecosystem altogether. By harnessing and further understanding the activity of these microbes, we can further understand and increase the efficiency of how we feed and reduce the amount of end waste that we have to deal with from that feed. By understanding and harnessing these wonderful microbes, we have unlocked potentially the key to making both our tanks and wild ecosystems healthier and more beautiful as a consequence. Thank you for being with us for this brief discussion of dennitrifying bacteria. And please join us next time on mastering microbes where we continue our discussion on the nitrogen cycle. We go into dazotrophy and amomox the ways in which different sets of other frontier microbes may participate integrally in the growth and health of wild corals, captive corals and wild ecosystems as a whole. Thank you. Please like and subscribe. Just like a dnitrifying bacteria, we crave malibidium, zinc, manganesees, and we need to be fed with subscribes, likes, and to fuel our our mission forward and be able to talk about microbes in the aquarium and aquaculture setting and spread this dialogue as far as we can. Thank you, and we will see you next time. [Music]