Mycorrhizae in the planted tank - irrelevant myth or further study needed?


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  • Oct 29, 2022
    Miami, FL

    Why should we care about what's happening in the planted aquarium substrate?​

    I think most of us intuitively know that the substrate microbiome is one of the least studied topics in the planted tank hobby. Many find it irrelevant as it seems to not be a determining factor for creating a healthy and vibrant aquarium. Others accept that a substrate microbiome develops over time in the aquarium and may contribute to the health of the plants. Again, a shrug of shoulders because, unlike adding CO2, it doesn't seem to make much of a difference.

    While I understand the above points, I believe that some hobbyists enjoy the science associated with our hobby and want to push forward our understanding of the living ecosystem we love to create. It's not an inanimate piece of art or a piece of furniture, we are all creating an environment for many forms of life and that responsibility requires that we try to understand and improve our knowledge of how to create the best environment we can.

    At the moment, we have little to know understanding of the relationship that the microbiome that develops in our substrates has with aquarium plants. We do know that this relationship has existed for eons and our only now learning how extensive it is. Could a plant that mysteriously isn't doing well in your tank be missing something like this? Could a healthy microbiome lead to stronger, healthier plants that better show color, fight of algae and grow?

    Take a listen to this Ted Talk when you have a little time. It's on the relationship of mycorrhizal fungi and trees but try to think about how it would apply to our planted aquariums.

    I previously linked a resource related to a study finding mycorrhizae in aquatic environments too. Here is another one talking about Lobelia and mycorrhizae.

    Businesses have been and are expanding their focus on the substrate microbiome​

    1_00.jpg Aqua Design Amano has for years been selling Bacter 100. According to them:
    Bacter 100 is a substrate additive, containing more than 100 kinds of substrate bacteria in a dormant state. By sprinkling on the base substrate, it can make an ideal substrate environment. By applying on top of blue green algae, it suppresses the growth of it.
    Anecdotally, I built a few ADA only aquariums in the past. I have yet to have an easier time with any of my other tanks. The ADA tanks that contained Bacter 100 and the other products, just ran and grew better.

    Snake oil? Is my experience, simply my experience and can be attributed to many things?

    I think in today's science, we know that monocultures of bacteria are bad so more bacterial species in harmony is better. We also know that bacteria and other microorganisms do a lot more in symbiosis than we first thought. We are learning this even about our own gut biome. Why do you think this wouldn't apply to our planted aquarium environments?

    Even CaribSea, a company that focuses on substrates, has quietly gotten into this with their product, Flora-Spore. I've reached out to them to get some background on this product but, alas, my requests have gone unanswered.

    According to their product labeling:
    Flora-Spore is a mixed blend of mycorrhizal species specially created to help create a thriving and dense root system in plants while increasing their ability to naturally extract elements directly from their substrate, allowing for better uptake of minerals from fertilizers. Mycorrhizal fungi have traditionally aided plants in widespread growth by acting as the intermediary between their roots and solid minerals. In the natural world, these organisms form a symbiotic relationship with most all vascular plants, making them a central component of the rhizosphere (the ecological zone existing around and influenced by roots and associated micro-organisms). Once they have colonized a root system successfully, mycorrhizal fungi secrete acids to dissolve surrounding minerals, which aids in increasing the efficiency of absorption of essential elements to the host plant. Recreate this natural (and hundreds of millions of years old) relationship in your habitat with CaribSea's Flora-Spore!

    I suspect that this product is similar to the TNC MycorrHydro produced for the hydroponics industry. Now I'm sure it's not the same but I think the intended purpose is similar. TNC says is also has hormones:
    TNC MycorHydro is a highly concentrated water dispersible mycorrhizal inoculant developed for hydroponic applications. It contains 15 different species of mycorrhizal fungi, including Endomycorrhizae and Ectomycorrhizae as well as 5 species of Trichoderma. It also contains 13 Bacillus species – Bacteria for Nitrogen fixing, Phosphorous solublising and growth promotion.

    TNC MycorHydro also contains natural bio-stimulants such as humic acid and derivatives of a natural marine algae (Ascophyllum nodosum). These include amino-acids, plant hormones – cytokinins, auxins and giberellins – as well as vitamins and trace elements.

    Is there an easy way to get some of the benefits without commercial products?​

    Think about this. What if I went over to @GreggZ's house and he was kind enough to share one cup of his substrate to me? I then came home and added that cup to my substrate. I've just taken a good sample of Gregg's microbiome and added it to mine simply adding to the diversity. However, as Gregg's tank is clearly successful, I'm willing to be that the microbiome that has developed in his tank is one that works well for our purposes. Why not "bottle the magic!"?

    Of course, this doesn't mean my tank will now be like Gregg's. This isn't DNA cloning. However, it does certainly function like me taking some probiotics. I'm adding bacteria, fungi, etc. that are beneficial.

    Let's extend this. Why wouldn't Marian Sterian or Dennis Wong not package up cups of their successful tank substrates and sell it to others? Wouldn't the same apply?
    Back on June 4, 2004, I made a link to this site on another forum: Mycorrhizae and hydrophytes.

    In the thread, our very own @plantbrain said the following:
    Actually roughly 50% of aquatic plants have been found to have fungal associations. There are several papers that looked at broad surveys. I have a paper on it floating around here somewhere.

    I identified a number of Exomychorrhizae on Bolbitus and I'm pretty sure there are some on Blyxa, Crinum, hairgrass and others.

    These do live in aquariums also.
    Our substrates are excellent for fungi, soil based substrates, antyhting anaerobic/low O2 is not good for fungi. They are obligate aerobes.

    I've even suggested that this association is part of why algae does not grow at higher O2 levels with plants.

    It can also explain and number of plants doing a little better after a little while of acclimation and why some plant cuttings from some folks do better than others.

    I saw several presentations of fungal associations at a wetland soils conference here last fall.

    Not many Mycologist running around.

    In year's past, it was assumed that fungal association did not really exist in submersed aquatics but they have found more lately and started to look into it more.

    Tom Barr
    At the moment, we have little to know understanding of the relationship that the microbiome that develops in our substrates has with aquarium plants. We do know that this relationship has existed for eons and our only now learning how extensive it is. Could a plant that mysteriously isn't doing well in your tank be missing something like this? Could a healthy microbiome lead to stronger, healthier plants that better show color, fight of algae and grow?
    Art I think this is a really valid topic.

    I've had times where I couldn't figure out what was going on and a really deep substrate vac reset the tank. I think the substrate health comes much more into play than we give it credit for.

    And I am very interested in the bacteria products. I have never tried one but would be interested to see what if any difference there may be. I have been known to use the everything but the kitchen sink approach so why not?

    Might be time for some new experiments in my tank!!
    Given the nature of the submersed conditions, fungi really cannot survive, only anaerobic bacteria are in the sediments below the top 1 cm for most sediments where aquatic plants exist. Fungi are obligate aerobes. There are very small high O2 rhizospheres surrounding the roots of aquatic plants, but th fungi could not extend beyond this region either, so offers little utility for for the plant's uptake. Bacteria is the name of the game. A stable roots system, a functioning layered bacterial systems(expressed by redox values for each functional bacterial reduction group) is what we have. Chytrids and a few others that like water a lot are all that really address aquatic systems, most all are also pest. The only cases I've test where for our ferns and epiphytic species which do not exist in low O2 or anaerobic condition. Bolbitus had healthy Ectomycorrhizae. In new ADA or similar ADA like aqua soils, the potential is there for more, but such aggegrates are not realistic in any natural system. Gravels, sure, but not "clay gravel", it's almost always a thick brick. If you wish test the plants, there are stains for the myco fungi. I'd wager they are almost all Ecto rather than Abuscular endo's. You need aerobic soil for that. "Aerial" water column roots have potential though. Periphyton itself has fungi, algae, micro fauna, a community within itself. If things go well there, then pest algae rarely take over. Water changes add O2 and give a quick boost to plants and the periphyton that's the healthy type, and kicks the pest algae's butt. Folks like to talk a lot about soil but hydric soils are very different and few bother to test, let alone even know what and how to look for the organisms of interest. You need a microscope and observe it. You need a good Redox probe set and a Redox meter. Some fungi stain. Some selective media for fungi culturing, sterile technique etc. All things many aquarist could potentially do, but not met any that have to date. Claus at Tropica did, I did, but not heard of anything since. The best Bible like book on Hydric soils would be Biogeochemistry of Wetlands by Reddy(My old wetland soil's professor at UF at Gainesville) and DeLanue. Covers almost all the important topics in the field of wetland soils.