Caribbean Biotope Seagrass Tank

[Michael Hoaster]

Greetings Saltwater Plant Experts!

I've been reading all the threads here on RC regarding marine planted tanks, and I must say, you guys are taking the hobby to another level! A lot of the biochemistry stuff goes right over my head, but I'm starting to get a feel for it. Some of these concepts are brilliant! For instance, dosing nitrate to balance its ratio to phosphate in a tank, thus favoring the plants over micro algae, that's way cool! So I know I'm in the right place to discuss my ideas for a Caribbean Biotope Seagrass Tank.

First, let me tell you a little about myself, before we get down to the dirty details. I started on the marine side in about 1993, with a 60 gallon cube with bleached coral skeletons and some pretty cool fish. In 2002, I began planning my dream reef tank. I ended up with a 240 gallon Eco-Wheel tank and a custom-built cabinet that I designed. When the economy tanked (sorry) in the late 2000's, my income dropped a lot, so it became increasingly difficult to justify the costs. Plus, I came to the realization that I might not be obsessive-compulsive enough to reach my goals as a reef keeper.

So, after some soul-searching, I decided to trade in my reef fish, corals, inverts, etc. for a Fresh Water Planted Tank. Much more affordable! For example: cost of fist-sized coral - $100, cost of a fist-sized plant - $5! And the aquascaping was much more interesting. So that's where I am now, with a pretty sweet freshwater planted tank setup.

But, like most of us in this hobby, I find it hard to leave well enough alone!

So here's what I'm thinking"¦

A Caribbean Biotope Seagrass Tank, with a deep sand bed, almost no live rock, lot's of manatee grass, a few sponges, gorgonians and anemones-and all endemic to the Caribbean! I want to combine everything I've learned from reef-keeping and plant-keeping.

I've also got lots of ideas regarding fish, plumbing, lighting, aquascaping, etc. but the first thing I'd like to discuss is the SUBSTRATE for the manatee grass.

I've got about 4 inches of very mature Eco Complete (a fresh water plant substrate) in the tank now. I'd like to use this as the foundation, so to speak, of my seagrass substrate. I've read that seagrasses like a rich, muddy, sandy substrate. So I'll mix in some fine aragonite and top it with progressively coarser sand, shells and rubble.

So, has anyone tried Eco Complete in a seagrass tank? Does anyone know of any reason why I shouldn't use it?

I look forward to your thoughts!

Thanks,
Michael

 

[Michael Hoaster]

Substrate for Seagrass

Substrate for Seagrass

Ok, so I did some research on Eco Complete. It's basically a lava-based sand/gravel of varied sizes. It's also basically inert, so doesn't directly contribute any nutrients. But it does have a high CEC, or cation exchange capacity, which (I think) means it can absorb/store nutrients that are added and release them as needed. Which I'm guessing (hoping) is a good thing.

So, overall, I'd say that Eco Complete is not as good a substrate as I'd hoped, but not a bad choice as a percentage of my substrate makeup. What I think helps favor MY Eco Complete, is the 5 or 6 years of accumulated mulm I've got in there. Yay pooh and stuff!

I'd welcome anyone else's thoughts, experiences, insights.

I really want to get this right, because I think getting the seagrass established is going to be one of the biggest challenges of this tank.

 

[Whiterabbitrage]

Following! Can't wait to see pix. This tank is going to be gorgeous.

 

[JLynn]

Sounds good! I can't see any reason why eco complete won't work either, just make sure to get live sand. You will need the worms and other infauna that come with it! Also, if you haven't already read it, take a look at this article: http://www.chucksaddiction.com/The Natural Reef Aquarium Part Two.html. It has lots of great info on seagrass beds.

 

[Michael Hoaster]

Seagrass Article

Seagrass Article

Wow! That was quite an article! Very helpful. Thanks JLynne!

One part I found particularly fascinating was about the different substrate compositions:

"The ability of a substrate to provide the essential dissolved nutrients has been shown to be determined by the composition of the sediment (Short 1987) in of its composition, either terrigenous (land-based eroded rock) or calcium carbonate. The grain sizes also determine the nutrient dynamics involved. It has been shown (Erftemeijer 1993) that Indo-Pacific, near-shore sediments comprised of terrigenous material has a significantly higher pore water concentration of nitrogen compounds than the calcium carbonate-based sediments while the reverse is true of phosphorous compounds."

So, the terrigenous substrate (like my eco-complete) holds more nitrogen, and the calcium carbonate substrate holds more phosphate. Having a good combination of these two substrates would seem to combine the best of both worlds. Also Eric Borneman's tip of using freshwater plant tabs to help the seagrass get started sounds like a great idea.

So here's what I'm thinking"¦

My substrate will have (more or less) 4 layers. Bottom layer: mulm-rich eco-comlete plus plant tabs. 2nd layer: very fine aragonite sand blended with eco-complete. 3rd layer: very fine aragonite sand. Top layer: a combination of fine and coarse sand, seashells and rubble.

I want to tip the balance in favor of the seagrass over the microalgaes, in the early phase of the tank. One of the strategies I learned from the freshwater plant side of the hobby, is to plant heavily, with fast-growing plants (along with the plants you really want) in the initial setup of the tank to get a leg up on the microalgae and cyanobacteria. As a variation on this technique, I may introduce lots of Manatee Grass, which is the plant I really want, without any other plants, which could compete with it. I want a large, monospecific seagrass bed in this tank. I'll introduce a crew of Astrea and Cerith snails to help out as well.

However, I'm tempted to follow Mother Nature's example and start with the pioneering species like oar grass and shoal grass. Once these get a foothold, I THEN bring in the Manatee Grass.

Another thing I noticed in the article was that he said that in the Indo-Pacific, the seagrasses had to take up almost all nutrients through their roots, because the water there is nutrient-poor. I wonder if caribbean seagrasses have more water-borne nutrients to work with (that will certainly be the case in my tank).

Thanks to all whom have read along so far. I invite you to chime in with your two cents!

 

[JLynn]

You're welcome! To the best of my knowledge, the main advantage of using pioneering seagrasses first is that they are shorter-lived than species like Thelassia Sp., so they build up a helpful layer of nutritious detritus in the sediment when they die. For that reason, it is worth considering. However, you mentioned that your eco-complete is very mature and has a lot of detritus built up in it already, so in your case the pioneering species of seagrass may be redundant.

 

[Michael Hoaster]

That thing about the nutrient-poor water column of the Indo-Pacific got me to thinking. What if I could emulate that in the initial phase of my tank? Isolate all the nutrients in the substrate to favor the seagrass, and keep the bulk water very low in nutrients to keep the algae at bay! Easier said than done right? Well, I don't plan to introduce ANYTHING before the substrate and seagrass. I do plan to bring a refugium online at some point. If I went ahead and brought it online from the start and stocked it with chaeto and ulva, that could help to keep nutrient levels down in my tank water, right? Sounds like a plan!

I know some of you are thinking "what about the live sand critters?" I plan to introduce them right after the seagrass - on the same day.

 

[Michael Hoaster]

Thanks, Whiterabbitrage for the encouragement! As soon as I have something to show, I'll post pics. As I'm still in the planning/dreaming phase, it'll probably be a while. In the meantime, there's much to discuss!

I do want to try and savor every step in the process, rather than rush through to get to the final result. I must say, I'm really enjoying this part - so many ideas swirling about! Now that I'm getting older and more experienced, I hope I have the patience to do this thing right.

As I've been compiling Caribbean wish lists of flora and fauna, I'm also thinking about the species of 'me'. I think a lot of us fail to consider ourselves in the equation. What are my characteristics as a mesocosm-keeper? I have to admit I'm kinda lazy! I like to use my big 'ol brain to figure out ways to save on labor. My favorite labor-saving device is NATURAL PROCESSES.

Does anyone out there remember reading Charles Mathews M.D.'s column, 'Reef Science', in "Freshwater and Marine Aquarium" magazine? His catchphrase was "Less technology, more Biology". He was all about using natural processes rather than gadgets. He also set up experimental aquariums to test all kinds of theories. I found this fascinating!

One of the things I was thinking about as I read through the "old favorites" in the Invert and Plant Forums, was the 'Nitrate to Phosphate Ratio'. Planted tanks with fish in them get plenty of phosphate through feeding and fish waste, so they tend to be nitrate-limited, right? Of course there's carbon and iron and other trace elements to consider as well, but for now I just want to focus on the N to P ratio. So the solution is to dose nitrate, right?

So I went to "the krib" website to check out their Poor Man's Dosing Drops formula. As I looked for that formula, I came across an article dated Sept. 1995, by Charley Bay, called "Nitrate Factories are Stupid". This article (rant) pretty much summed up the thought that started the move away from trickle filters back in the day.

Do you see where I'm going with this?

As I see it, I have two choices here: I can go to town and find all the ingredients for the PMDD, mix it up and start adding daily dosages to my tank, OR, I can go up in the attic and dust off the "'Ol Nitrate Factory". Yep, I'm seriously considering putting my trickle filter back into service! And IF it turns out to work, I'm going to write an article titled "Nitrate Factories are Freaking Brilliant".

One unfavorable comparison I can think of is the fact that with dosing, you can adjust the N ratio pretty easily to suite your tank's needs. I suppose I could adjust the number of bioballs in the trickle tower to raise or lower the amount of nitrate produced in "the factory". Hmm"¦

OK, so am I missing something? Please, someone, shoot this theory down before I make a fool of myself!

 

[JLynn]

I know some of you are thinking "what about the live sand critters?" I plan to introduce them right after the seagrass - on the same day.

The problem with that plan is that there is nowhere to buy these "live sand critters." The only way to get these infauna is to get them with the sand, and for the long-term health of your sand bed, it is vital that you do. These creatures won't add nutrients to the water column; they have their own food web in the sand. On that note, do not get one of those sealed bags of sand that is called live sand. What they mean by that is that it contains bacteria. You will need to order your sand online in order to get the good stuff (eg the sand with bacteria and worms and other sand-dwelling creatures vital to your tank).

 

[Michael Hoaster]

JLynn, there is a source for sand bed critters without the sand. Indo-pacific Sea Farms (ipsf.com) They have all manner of sand dwelling creatures, including worms, mini brittle stars, tiny clams and what not. Inland Aquatics (inlandaquatics.com) also carries them. I probably will buy some caribbean live sand as well. I found a source in Florida that sells actual live sand from the ocean, so I'll have some sand specific to my caribbean biotope.

I think I'm going to add the top 3 layers of sand AFTER I place the manatee grass on/in my bottom layer, so as to avoid doing any damage to the roots. I'll mix in that Florida live sand with the top layer and then I'll introduce the pods, worms, etc.

Oh, I wanted to thank you for your thoughts on the pioneering seagrass idea. I agree that, with all the mulm I've already got, they may be redundant.

 

[houstonhobby]

I will follow your efforts so please keep us posted with pics. Went snorkeling in Mexico once over grass beds and was blown away by the beauty of it, but I spent a lot of time on planted tanks and discovered I had no real talent for it so I won't try one myself.

There are unique animals in an environment like this. That is one of the things that could make it really special.

 

[Michael Hoaster]

Thanks for the post, HoustonHobby! Yes, I'll post pics when I have something to photograph. Right now I'm still looking at my quickly overgrowing freshwater planted tank"¦

I guess the first thing I'll have to photograph is kind of an oddball project for the new tank.

I've got one of those Tunze powerheads that is mounted on the top of the tank, so it hangs down into the water, looking rather unnatural. And I'd really like to not have ANY visible plumbing or gadgets in the tank. But I also really want to keep that powerhead right where it is.

So I'm going to build my own aquarium ornament to hide it. What kind of ornament? Well, in keeping with my caribbean biotope theme, I'm going to sculpt a mangrove stump with roots. The top part of the stump, which will extend up a little above the water level, will be hollow, so as to accommodate the powerhead. The roots will arc out reach down into the substrate.

If you google mangroves, check out some of the images. The roots of these trees are just beautiful! I hope to capture some of that beauty with my fake stump"¦

 

[JLynn]

Sounds good! The ceramic will have the added benefit of housing more bacteria. I do love mangroves. I only wish I had the patience to grow one big enough to recreate that environment!

 

[Michael Hoaster]

The 'Ol Nitrate Factory

The 'Ol Nitrate Factory

I'm still hoping to get some comments on my idea of using a trickle filter to save me the trouble of dosing nitrate. As I said before I'm kinda lazy, and I know from experience that I'm not likely to keep up with daily dosing.

Also, any thoughts on using chaeto and ulva in the 'fuge right from the start to keep water column nutrients to a minimum, while the seagrasses suck up nutrients from the substrate? I thought this strategy would help to minimize that early microalgae phase.

I'd appreciate any thoughts, ideas, suggestions you might have.

 

[3D-Reef]

If you can find it,there was a study done by Jose Gonzalez Liboy (2005)on the Caribbean grass Thalassia,t.It has just the info Your looking for.

From the study....41% is sand,17.5% silt,32% clay with small amounts of quarts.In an other study they found that there was 80% calciumcarbonate,~18% mag-calcite,~2% nutrient rich mud/soil.

The only thing I see,that might be problem,is that if you put too much nutrient rich material in the substrate it can,and most likely,will go anoxic and kill the grass.

One other thing,most seagrass beds tend to become more richer in nutrients over time.So if you start out with a very rich environment,then it can become eutrophic in a short period of time.

 

[Michael Hoaster]

Thanks, 3Dreef. I'll see if I can find that study.

Basically, it sounds like you're suggesting I use less organic-rich substrate (my aged eco-complete), to avoid anoxic conditions (nearly zero oxygen) in the sand bed and eutrophic (nutrient-heavy) conditions too soon, rather than letting them build up naturally, correct?

I would expect anoxic conditions at the bottom of my sand bed, that I estimate will be around 7 inches deep. But I wouldn't expect that to kill my seagrass. Can you elaborate? I would imagine that in nature anoxic conditions exist at similar depths without it doing harm to the grasses.

That's a very good point about eutrophic conditions too quickly. Maybe I'm trying to give them too much of a good thing too soon? And I definitely don't want all that stuff seeping out into the water column right away and causing eutrophic water conditions! Algae-fest!

I'm hoping that my 4 layer substrate plan allows a wide gradient of oxygen levels through its depth, while keeping the really nutrient-rich area at the very bottom, and not up in the water column.

And just in case, my fuge with chaeto and ulva should help in that regard.

Thanks for your insights! More please!

 

[Michael Hoaster]

3DReef, I found that study and I'm reading it now. Thanks for the info!

 

[Michael Hoaster]

I read the study on thalasia in Puerto Rican waters. In it there was a good chart of sediment composition in different areas. So yes, not a whole lot of mud in there. I wish he had discussed it a bit more. The seagrass article from Chuck's Addiction had some really informative discussion on the application to our tanks, plus a good quote from Ron Shimek:

"Sediments - The seagrass refugium's sediment is vital to the health and long term survival of the seagrass just as it is in natural meadows. How you construct the sandbed is going to determine its functionality in providing a nutrient rich environment for the seagrasses rhizomes and root structures. Seagrasses are plants that depend upon their roots for the uptake of nutrients, roots that require extremely fine grain sizes, it will be imperative that a calcium carbonate substrate with grain sizes ranging from 0.2 - 1.02mm be used with a depth of no less than six inches, deeper if possible. Incorporating a live mud into the sediment during the sand beds construction will ensure a suitable number of infauna are introduced. Just as in nature the infauna are critical to the functionality of any sandbed to process nutrients and prevent the formation of sand clumps by their movement through the sediment (Shimek 2001)."

 

[3D-Reef]

Thanks, 3Dreef. I'll see if I can find that study.

Your welcome!

Basically, it sounds like you're suggesting I use less organic-rich substrate (my aged eco-complete), to avoid anoxic conditions (nearly zero oxygen) in the sand bed and eutrophic (nutrient-heavy) conditions too soon, rather than letting them build up naturally, correct?

Correct.

I would expect anoxic conditions at the bottom of my sand bed, that I estimate will be around 7 inches deep. But I wouldn't expect that to kill my seagrass. Can you elaborate? I would imagine that in nature anoxic conditions exist at similar depths without it doing harm to the grasses.

It's not so much that the lack of O2 causes harm to the plant,(the plants have a way of around that) but, it's more about what is happening in an anoxic environment that gets 'em.
Seagrass plants, more or less, depend on/need too interact with the bacteria there to release nutrients too them.They are kinda lazy in that aspect.They could do themselves,but at a cost.So,if there are more bacteria/nutrients than what the grass can support with O2/NO3 the bacteria then turn too SO4 (sulfate).
When the bacteria start using SO4 ...the end result is Hydrogen-sulfide,or bi-sulfide.This gas is highly toxic to everything alive including plants.
Basically it will suck out any oxygen from anything alive.This is what kills the plant.

That's a very good point about eutrophic conditions too quickly. Maybe I'm trying to give them too much of a good thing too soon? And I definitely don't want all that stuff seeping out into the water column right away and causing eutrophic water conditions! Algae-fest!

Tip of the day
"First,it has to be acknowledged that seagrasses seem to be adapted for growing in nutrient-poor environments.Not only the mechanisms described in the first sections of this chapter (nutrient resorption,use of poor water nutrients,storage,ect.) allow these plants to better use nutrients,but also it has to be considered that seagrasses require approximately 8-50 times less nitrogen and 1.5-100 times less phosphorus for daily growth than macroalgae or phytoplankton,respectively (Daurte,1995)."

I'm hoping that my 4 layer substrate plan allows a wide gradient of oxygen levels through its depth, while keeping the really nutrient-rich area at the very bottom, and not up in the water column.

And just in case, my fuge with chaeto and ulva should help in that regard.

Thanks for your insights! More please!

 

[3D-Reef]

I read the study on thalasia in Puerto Rican waters. In it there was a good chart of sediment composition in different areas. So yes, not a whole lot of mud in there. I wish he had discussed it a bit more. The seagrass article from Chuck's Addiction had some really informative discussion on the application to our tanks, plus a good quote from Ron Shimek:

"Sediments - The seagrass refugium's sediment is vital to the health and long term survival of the seagrass just as it is in natural meadows. How you construct the sandbed is going to determine its functionality in providing a nutrient rich environment for the seagrasses rhizomes and root structures. Seagrasses are plants that depend upon their roots for the uptake of nutrients, roots that require extremely fine grain sizes, it will be imperative that a calcium carbonate substrate with grain sizes ranging from 0.2 - 1.02mm be used with a depth of no less than six inches, deeper if possible. Incorporating a live mud into the sediment during the sand beds construction will ensure a suitable number of infauna are introduced. Just as in nature the infauna are critical to the functionality of any sandbed to process nutrients and prevent the formation of sand clumps by their movement through the sediment (Shimek 2001)."

I agree,Shimek is an expert on sand beds and infauna and I give Him all due credit and respect,but,even He Himself will tell you He's not up on grasses and there requirements.With that said...Seagrasses can and do uptake nutrients from the not only from the substrate but from the water column as well.Equally I might add.
So IMO,it would be easier to manipulate nutrients in the water column than in the substrate.Because once it's in there...it's there until you tear it down and start over.