Anyone want to study refugium plants with me?

[OnlyGenusCaps]

Hi all. I'm so excited there is a specific science section here! ?‍?

I'm in the dreaming and designing phase for my next tank. I'm a bit overkill with filtration when I set up a tank. Always have been. I'm learning there are down sides, but that's another story... In designing the sump for my new tank, it's pretty clear what the evidence suggests to use for the biomedia. But, as we all know, that brings you to nitrates. I've not yet figured out how to have high flow and anoxic conditions to promote enough denitrifying bacteria, plus that would still leave build ups of other elements like P, etc. So, I think having a refugium where you can toss out biomass on the regular to export nutrients from the system makes decent sense.

I had a small discussion with Dave over on aquarium science about this, but that's not a forum. I've recently become focused (read: obsessed) with trying to find an optimal species of plant to grow in a refugium that would allow me to export unwanted nutrients. I've been keyed in on Salvinia sp. because of their high growth rates, and that they can be 3-5% N by dry weight according to various studies. Additionally studies looking at the invasive potential (these are mostly for Salvinia adnata Desv. syn. Salvinia molesta D.S. Mitch.) suggest they respond strongly to increasing N availability in both biomass production and by increasing the mg of N/g dry mass. That's a great positive feedback if you want to export nutrients via Salvinia and a terrible one if you want to control an invasive species. Plus the system was not particularly pH sensitive, and growth was optimal right near aquarium temperatures. Perfect. So, I had it right? Well then I came across this:

Uptake rates of nitrogen and phosphorus in the water by Eichhornia crassipes and Salvinia auriculata. Petrucio & Esteves (2000) Rev. Brasil. Biol., 60(2): 229-236

So, now I am questioning whether Salvinia are the right choice or if I should set it up for Eichhornia which pulls more from the water column. There are of course a number of other issues in terms of tissue N content and productivity under refugium conditions. But I am curious, has anyone else been researching this? Or is this my own windmill to tilt at? Anyone want to research the optimum refugium plant with me?

 

[eatyourpeas]

Where does Hornwort fit in this project? I have had amazing results with it.

 

[Retired Viking]

I have salvinia floating in my 55 gallon tetra tank. To be honest all I know is it absorbs the ammonia my fish produces and is green and turns brown when it dies. I leave the tank water low so the light reaches most of the salvinia and it gives shade to my tetras. Sorry I am not much help for your research, I wish you good luck.

 

[GuppyBreeder180604]

Hi all. I'm so excited there is a specific science section here! ?‍?

I'm in the dreaming and designing phase for my next tank. I'm a bit overkill with filtration when I set up a tank. Always have been. I'm learning there are down sides, but that's another story... In designing the sump for my new tank, it's pretty clear what the evidence suggests to use for the biomedia. But, as we all know, that brings you to nitrates. I've not yet figured out how to have high flow and anoxic conditions to promote enough denitrifying bacteria, plus that would still leave build ups of other elements like P, etc. So, I think having a refugium where you can toss out biomass on the regular to export nutrients from the system makes decent sense.

I had a small discussion with Dave over on aquarium science about this, but that's not a forum. I've recently become focused (read: obsessed) with trying to find an optimal species of plant to grow in a refugium that would allow me to export unwanted nutrients. I've been keyed in on Salvinia sp. because of their high growth rates, and that they can be 3-5% N by dry weight according to various studies. Additionally studies looking at the invasive potential (these are mostly for Salvinia adnata Desv. syn. Salvinia molesta D.S. Mitch.) suggest they respond strongly to increasing N availability in both biomass production and by increasing the mg of N/g dry mass. That's a great positive feedback if you want to export nutrients via Salvinia and a terrible one if you want to control an invasive species. Plus the system was not particularly pH sensitive, and growth was optimal right near aquarium temperatures. Perfect. So, I had it right? Well then I came across this:

Uptake rates of nitrogen and phosphorus in the water by Eichhornia crassipes and Salvinia auriculata. Petrucio & Esteves (2000) Rev. Brasil. Biol., 60(2): 229-236

So, now I am questioning whether Salvinia are the right choice or if I should set it up for Eichhornia which pulls more from the water column. There are of course a number of other issues in terms of tissue N content and productivity under refugium conditions. But I am curious, has anyone else been researching this? Or is this my own windmill to tilt at? Anyone want to research the optimum refugium plant with me?

I have had experience with Salvinia and let me tell you they do reproduce like crazy and they do eat up a lot of nutrients, also they can survive in really low light conditions so it can be a good option, but I would also say to use najas guadalupensis as they also eat a lot of nutrients and reproduce crazy fast and if you use both then you could have the Salvinia on the top and the najas on the middle and bottom both consuming extra nutrients all over the water column of your refugium and if you used it for some animal (as the name refugium would suggest) then the najas would provide a sense of cover and it would help to break the line of sight to reduce stress.

 

[Colin_T]

Any floating plant will use nutrients (usually ammonia before nitrite and nitrate), as well as any other nutrients in the water.

There shouldn't be much phosphorus in the water.

 

[eatyourpeas]

One of the Najas is considered noxious species in Washington State, so I was looking that up. It is the Najas Minor.

 

[OnlyGenusCaps]

I have had experience with Salvinia and let me tell you they do reproduce like crazy and they do eat up a lot of nutrients, also they can survive in really low light conditions so it can be a good option, but I would also say to use najas guadalupensis as they also eat a lot of nutrients and reproduce crazy fast and if you use both then you could have the Salvinia on the top and the najas on the middle and bottom both consuming extra nutrients all over the water column of your refugium and if you used it for some animal (as the name refugium would suggest) then the najas would provide a sense of cover and it would help to break the line of sight to reduce stress.

I'd not thought about a submerged layer. It's true a "community" of plants may be more effective than a single species. There's research on at least terrestrial communities that suggests that. Thanks!

Where does Hornwort fit in this project? I have had amazing results with it.

I'd focused at first on emergent plants (those being ones with their photosynthetic tissues in the air in this case) because they are not dependent on the CO2 in the water, so they are unlikely to be limited by the resource. I've had issues with hornwort over growing tanks rapidly though, so when I explore the prospects for a submerged component, they might be interesting. From my memory, they don't do as well in lower light though, which might preclude them as the top layer is most important here. Thanks for the suggestion!

I have salvinia floating in my 55 gallon tetra tank. To be honest all I know is it absorbs the ammonia my fish produces and is green and turns brown when it dies. I leave the tank water low so the light reaches most of the salvinia and it gives shade to my tetras. Sorry I am not much help for your research, I wish you good luck.

Thanks for the well wishes! Good to know about your experience with Salvinia growing so rapidly in an aquarium. That's useful.

Any floating plant will use nutrients (usually ammonia before nitrite and nitrate), as well as any other nutrients in the water.

There shouldn't be much phosphorus in the water.

Agreed any floating plant will use the N in the column, with a preference for the available ammonium - AFAIK. But, I'm curious what the differences are in terms of exporting nutrients. How much unwanted N can I move out in a decent sized refugium? And are those species differences substantial? That's what is motivating me here.

Also, Perth, WA?! I love Perth! I'd move to Perth in a heartbeat and never leave. Ever! Although specifically Mandurah stole my heart. Sitting at the Dome by the marina having a flat white. I was supremely content. I'm a bit jealous. Sorry.

 

[eatyourpeas]

I currently have duckweed on the top layer, followed by Hornwort. It seems to still get enough light and provides a nice cover for the lower layers. Pothos is my other go-to, and I have that in the corner of the tank near the filter intake where it can benefit from the waste flowing in its direction. I do have these in the tank, not in a refugium, so am curious as to how they would work in the sump. Will you be looking at underwater lighting? That could solve the layer problem.

 

[GuppyBreeder180604]

I'd not thought about a submerged layer. It's true a "community" of plants may be more effective than a single species. There's research on at least terrestrial communities that suggests that. Thanks!

Yes, think of it as a rainforest.
The Salvinia is the canopy, the emersed part of rotala for example is the emergent layer, the najas are the understory and the green or brown algae that will inevitably grow on the bottom is the forest floor.
And it would work just like one, as you'll see, the more variety of plants exists in an ecosystem the better the nutrients are managed as 1 single species of plant will compete for the same nutrients with itself and will eventually die or reduce its population, on the other hand when there is a variety of plants on different levels they compete for nutrients on different ways thus using most of them in a better way that allows all the plants to reach a balance of population with each other, and to better eradicate those pesky nitrates, nitrites, ammonia and phosphorus. And just like in the case of rainforest the more variety of plants there is the more life it can sustain (fish fry, shrimps, snails, injured fish, etc.).
if you ask me the best plants would be Salvinia natans, water lettuce, rotala rotundifolia, najas guadalupensis, Egeria densa, pearlweed, ludwigia repens, and green algae. With that, you should have a refugium full of life and housing for your fish and invertebrates.

 

[Colin_T]

Also, Perth, WA?! I love Perth! I'd move to Perth in a heartbeat and never leave. Ever! Although specifically Mandurah stole my heart. Sitting at the Dome by the marina having a flat white. I was supremely content. I'm a bit jealous. Sorry.

I'm in Mandurah now, it's a dump, so is Perth. There have been hot dry easterly winds since August (they don't normally start till mid January) and the town is covered in dust. It hasn't rained for months and it's just unpleasant.

I have to wipe my car windows down with a damp paper towel any time I want to use my car because it gets coated in a layer of brown and grey dust in 24 hours. The other day when I was outside there was literally a 3-4mm layer of dust on the car, and it was from one night.

re: plants, you can grow the floating plants in the main tank too and they should reduce any nutrients.

 

[OnlyGenusCaps]

I'm in Mandurah now, it's a dump, so is Perth. There have been hot dry easterly winds since August (they don't normally start till mid January) and the town is covered in dust. It hasn't rained for months and it's just unpleasant.

I have to wipe my car windows down with a damp paper towel any time I want to use my car because it gets coated in a layer of brown and grey dust in 24 hours. The other day when I was outside there was literally a 3-4mm layer of dust on the car, and it was from one night.

re: plants, you can grow the floating plants in the main tank too and they should reduce any nutrients.

I remember there were a number of buildings in Mandurah away from the water front that were closed down. One in particular, little tan stucco building, that had on it's side that it had been a beauty parlor, lunch counter, and appliance repair shop (or some similar set of wide ranging services). I took a photo because all I could think was "how could a place that that not offer what people wanted?!" Yes, there dusty stretches, but I lived in the Sonoran Desert for years and loved the quirky and sometimes shabby nature of the places there. I realize that that part of WA should not be as bad as the desert, but climate change is not predicted to be kind to Oz in general. I'll admit, unfavorable as the weather is here (35 in the summer and -30 in the winter), it's pretty water secure for the future. So I guess at least there is that. Still I loved WA. Felt like returning home to a place I'd never been when I first got there. Never experienced any feeling like that in any of my other travels.

In terms of plants, I agree they'll take up N anywhere they are grown. But, I'm planning this for an African cichlid tank where I intend to use none in the display. Plus, I don't like how floaters clog my overflow in the main tank. I suppose my though it pinning down an optimal regufium species would allow more freedome in the display tank.

I currently have duckweed on the top layer, followed by Hornwort. It seems to still get enough light and provides a nice cover for the lower layers.

Good to know the lighting requirements can be met there. I have hornwort growing under water lilies in a tub in a greenhouse, but the sun is a bit more intense than my aquarium lighting.

Will you be looking at underwater lighting? That could solve the layer problem.

I'm not planning on it. Adding the supplemental lighting will already consume more power and add more heat. I'd like to make this as straightforward of a system as possible.

And it would work just like one, as you'll see, the more variety of plants exists in an ecosystem the better the nutrients are managed as 1 single species of plant will compete for the same nutrients with itself and will eventually die or reduce its population, on the other hand when there is a variety of plants on different levels they compete for nutrients on different ways thus using most of them in a better way that allows all the plants to reach a balance of population with each other, and to better eradicate those pesky nitrates, nitrites, ammonia and phosphorus.
if you ask me the best plants would be Salvinia natans, water lettuce, rotala rotundifolia, najas guadalupensis, Egeria densa, pearlweed, ludwigia repens, and green algae. With that, you should have a refugium full of life and housing for your fish and invertebrates.

If I understand you correctly you are arguing for the diversity-stability hypothesis. I certainly have colleagues who are big proponents of that and have shown it can be true. People seem to want that to be true as well, especially those who are conservation minded. However, it's far from settled as uniformly true. You and I could ping-pong references from the primary literature back and forth at each other ad infinitum in support and in opposition to that hypothesis at this stage. Don't get me wrong, it's is a valuable line of inquiry in relation to refugia in aquariums. But, I think we've gone down the garden path here a bit from my original line of inquiry. I am attempting to find the species that is most efficient at removing unwanted N from a tropical, freshwater aquarium when its biomass is pulled on a regular basis. Yes, more species might do so more efficiently than a single species if for no other reason that a second species might allow for greater total biomass production. However, that greatly complicates any tests and I don't think we have a stating place to jump off from for that at this point. I am trying to learn about what might be that jumping off point. Who is most efficient solo. However, if you know of primary literature examining species complexes as they would relate to a refugium, I'm always happy to be wrong.
Thanks for the list of possible species to combine! If and when I get to the point of examining species combinations, that's a great list to begin exploration from.

 

[GuppyBreeder180604]

If I understand you correctly you are arguing for the diversity-stability hypothesis. I certainly have colleagues who are big proponents of that and have shown it can be true. People seem to want that to be true as well, especially those who are conservation minded. However, it's far from settled as uniformly true. You and I could ping-pong references from the primary literature back and forth at each other ad infinitum in support and in opposition to that hypothesis at this stage. Don't get me wrong, it's is a valuable line of inquiry in relation to refugia in aquariums. But, I think we've gone down the garden path here a bit from my original line of inquiry. I am attempting to find the species that is most efficient at removing unwanted N from a tropical, freshwater aquarium when its biomass is pulled on a regular basis. Yes, more species might do so more efficiently than a single species if for no other reason that a second species might allow for greater total biomass production. However, that greatly complicates any tests and I don't think we have a stating place to jump off from for that at this point. I am trying to learn about what might be that jumping off point. Who is most efficient solo. However, if you know of primary literature examining species complexes as they would relate to a refugium, I'm always happy to be wrong.
Thanks for the list of possible species to combine! If and when I get to the point of examining species combinations, that's a great list to begin exploration from.

Yes, I am talking about diversity-stability, and even tho I love this theory I know that going only from written sources isn't viable so I am also talking from experience, not only in the aquarium but also in other areas like ponds and home-level agriculture. I have at the moment my read-eared slider in 55 gallons and I know it's small for her but I will upgrade, and even tho I have no biological filtration in my "filter" I do have a lot of Salvinia, water hyacinth, water lettuce, najas, and egeria. And I never do water changes, and when I test my water the values always come at 0ppm when it comes to the common dangerous chemicals, at first I only had water lettuce and najas and the water turned green from excess chemicals, then I changed to Salvinia and the water was still green, then I made my current mix and no green water and no dangerous chemicals in my water.
For my home-level agriculture, I find that a raised bed can be used for much longer and produce more food when you plants more than 1 variety of plants, good mixes, for example, are corn and squash, tomato and beans or peppers and peas since once again a variety of plants allows the nutrients to be used more efficiently and prevents pest plants from taking over.
I am glad that you will consider the plants on my list and as such I will give you a little experiment that I made:

In a 5 gallon container with a set temperature of 25 degrees celsius and light for 12 hours per day you will add some food and let it rot to release the dangerous chemicals and measure their levels, I use tetra 6 in 1 strip to measure the levels of the chemicals that should look like this, nitrate: 80-100 ppm, nitrite: 1-5 ppm, and chlorine (which also measures ammonia): 0.5-1 ppm. Once you have archived those parameters you will add your plants of choice, I decided to go by weight (so if you use 500 grams of Salvinia you have to use 500 grams of everything else) and give it 2 weeks to see how it lowers the levels of chemicals and how much the mass increased, based on that you can see which plants work the best for you in removing chemicals and creating biomass.

 

[OnlyGenusCaps]

Thanks for your reply and sharing your experience! It is an interesting anecdotal case in your tank. I do like the little experiment, too! I'd love to see the results as a factorial design with the different species. It would give an idea of which species are the primary drivers of the consumption, and whether there is non-linearity (i.e. whether species work better as a system, or indeed inhibit one another). Of course, for some of these species the work has been done (I have a few references for anyone interested) and at lower initial nitrates which more closely match natural and aquarium water conditions. That said, one of the aspects I am missing is which species can draw the nutrients down lowest - or has the lowest R* for nitrate. That of course may or may not be the species that performs best at higher nitrate levels. This could result in having a pairing of species that might function better (assuming that the species with the lowest R* doesn't out compete the other plant by depriving the other of N).

So, to me there are two issues at hand. The first is, which species sequesters the maximum amount of N, especially from nitrate, allowing that surplus N to be exported from the system as biomass. The second is, if the goal is to scrub the nitrates as low as possible, which species can pull the nitrate concentration down the lowest from the water column. It's entirely possible that because of physiological and life history trade-offs these two aspects will not be found in the same species. From there, I would feel comfortable combining those species to see what if any interactive impacts occur.

I'll admit, I am getting tempted to try this experiment. Actually, @GuppyBreeder180604 's suggestion of using a 5 gal bucket makes it more feasible. That was a great call. But before I commit time and treasure to such an endeavor, I'm headed back to the literature.

 

[GuppyBreeder180604]

Thanks for your reply and sharing your experience! It is an interesting anecdotal case in your tank. I do like the little experiment, too! I'd love to see the results as a factorial design with the different species. It would give an idea of which species are the primary drivers of the consumption, and whether there is non-linearity (i.e. whether species work better as a system, or indeed inhibit one another). Of course, for some of these species the work has been done (I have a few references for anyone interested) and at lower initial nitrates which more closely match natural and aquarium water conditions. That said, one of the aspects I am missing is which species can draw the nutrients down lowest - or has the lowest R* for nitrate. That of course may or may not be the species that performs best at higher nitrate levels. This could result in having a pairing of species that might function better (assuming that the species with the lowest R* doesn't out compete the other plant by depriving the other of N).

So, to me there are two issues at hand. The first is, which species sequesters the maximum amount of N, especially from nitrate, allowing that surplus N to be exported from the system as biomass. The second is, if the goal is to scrub the nitrates as low as possible, which species can pull the nitrate concentration down the lowest from the water column. It's entirely possible that because of physiological and life history trade-offs these two aspects will not be found in the same species. From there, I would feel comfortable combining those species to see what if any interactive impacts occur.

I'll admit, I am getting tempted to try this experiment. Actually, @GuppyBreeder180604 's suggestion of using a 5 gal bucket makes it more feasible. That was a great call. But before I commit time and treasure to such an endeavor, I'm headed back to the literature.

Sounds good, the more knowledge you have before experimenting the easier it will be to interpret the results to find the best plants for you.

one of the aspects I am missing is which species can draw the nutrients down lowest - or has the lowest R* for nitrate. That of course may or may not be the species that performs best at higher nitrate levels. This could result in having a pairing of species that might function better (assuming that the species with the lowest R* doesn't out compete the other plant by depriving the other of N).

then do the experiment 3 times, one with high N levels, one with low N levels, and one were you mix the plants that performed the best in the high N with the ones that performed best in the low N in a medium N level to see if they out-compete each other or if they reach a balance since the balance would mean that mix of plants is the best for you and it will yield the best results.

 

[eatyourpeas]

One quick question from an ignorant bystander: how would you match the ideal water parameters for all these plants if you are going with a cichlid tank?