Caribbean Biotope Seagrass Tank

[houstonhobby]

You mentioned a few posts back that once you build the substrate the nutrients that are in it are there for life so you plan to just manipulate the nutrients in the water column.

As a former planted tank person I think this may be a mistake. First, nutrients do move back and forth between the water column and the sand bed. But more important, if your seagrass is used to getting nutrients from the sediments then forcing it to compete with nutrients only in the water column is probably a bad idea.

In the water column, all sorts of micro and macro algae can get at the nutrients, probably easier than the sea grass can. To help the sea grass outcompete these undesirables, you need to help them out by feeding the roots.

One thing that planted tank people do is put nutrients into clear gell caps (the sort of thing health food stores carry) and then push them into the substrate near the roots of the plant they want to feed. I think you should consider something like this.

Thanks,
Rod

 

[Michael Hoaster]

HoustonHobby, I agree. I think that was someone else who posted about feeding the water rather than the substrate. I want my water as nutrient poor as is practical for this application.

Basically I want to start this tank doing everything I can to favor the seagrasses and starve the algae and cyanobacteria. I want to confine the nutrients to the substrate as best I can. I like your idea of using gelatin caps to fertilize the roots. Sort of like the plant tabs, but you're able to custom-taylor the nutrients you want in there.

I'm going to set up a refugium as well with chaeto and ulva to help soak excess nutrients.

I am currently a freshwater plant person myself, with a 240 gallon tank with metal halide lighting, CO2, and a whole lot of plants! As I've been planning this new tank, I've been letting the plants get out of hand!

As I said back in the beginning of this thread, this tank started as a reef tank, then I changed over to FW planted. Now I want to combine what I've learned on the reef side and the FW planted side to make this SW seagrass dominated tank.

Here's a pic of my current tank, left 2/3s of it.

I appreciate your thoughts. Keep 'um coming!

 

[houstonhobby]

You obviously have the talent for this. None of my planted tanks ever looked that good. Thanks for the pic.

 

[Michael Hoaster]

Wow thanks, HoustonHobby for the compliment! You made my day.

By the way, what did you put in the gel caps for your plants?

 

[3D-Reef]

Seagrasses out compete algae by recycling what little nutrients that are available to them.The less there is in the substrate...the less there is too leach out into the water column.
The plants already uptake from the water column.It's how they compete with algae.By sucking the nutrients down below what algae can survive.

If you put in more nutrients than what the plants need to recycle.Your only going to feed the algae/cyano.
Just saying.

 

[houstonhobby]

I never made caps of my own. I bought them already made from a guy on the plantedtanks forum who made them up for fresh water. I have no idea if salt water formulas would be different but I doubt it. I bought dry ferts from some place I can't remember but it is an easy google. I used them to dose the water column but you could put them in caps easily. I got gell caps from amazon prime and use them myself for medical purposes.

 

[Michael Hoaster]

Thanks 3D-Reef. That really is the key I think. How much nutrients to provide the seagrass at startup, to give them a head start without giving algae what it wants. It seems to me that putting the nutrients deep in the sand bed, while minimizing water column nutrients is a good solution. I agree that they will leach out into the water, but hopefully that will take some time, and give the seagrass a head start.

You said before, once you put something in the sandbed, it's there until you break down the tank. I get your point but on the other hand, I've added heavy nutrient input to my freshwater planted tank substrate, using plant tabs. The plants suck them up and grow like weeds, then slow down as the tabs get used up. I pushed them down about 5 inches deep, and I did not notice any uptick in algae production in the tank. I'm sure some leached out, but overall the strategy worked. My plants outcompeted the algae.

I realize of course these are different plants, but I know that plants will use nutrients that are available to them, even if they are adapted to nutrient-poor conditions. Diana Walstad did some experiments that proved this pretty convincingly. Her book "The Ecology of the Planted Aquarium" is excellent.

I do agree with you that putting too much of my aged eco-complete in there would be a mistake. I'm just going to have to (re)read all I can find about seagrass substrates in nature and come up with my own secret sauce. If I recall, some exist in nutrient-poor substrates and some in nutrient-rich ones.

I think our biggest difference of opinion is on the seagrass' ability to take up nutrients from the water column. Here's my point of view: these are higher plants with separate components that do different things. Basically, the roots take up nutrients and the leaves photosynthesize. They are not macroalgae, which are much simpler plants that do get most of their nutrients from the water column. So in my opinion, feeding the roots and not the bulk water is the best way to favor the seagrass.

 

[jpappy789]

I'm just going to start thinking out loud here...as someone with ZERO firsthand experience growing seagrass, but is coming from a similar place as you (FW planted tanks) and is trying to start a seagrass tank. I'm also a "soil scientist" with specific interests in aquatic/wetland systems, so I have some theoretical background as well.

Even the fine ecocomplete is supposed to be around 0.5-3 mm, which actually may be a bit coarser than what you could see in a typical seagrass bed (depending on the location, you'd obviously want to focus on the Carib. areas). I'm honestly not sure how much of a difference it would make, but you probably wouldn't want to overdo it compared to some finer grains.

Regarding the nutrient issue, yes, "higher order plants" have roots for a reason but when it comes to aquatic plants that doesn't mean it's their exclusive means of nutrient uptake. The aquatic environment is different than the terrestrial, where water conservation is at a premium.

Interesting article I found with a quick (emphasis on quick) Google search: http://www.int-res.com/articles/meps/134/m134p195.pdf

Pesky kinetics aside, it seems that (for this particular species and location at least) leaf uptake is oftentimes needed because the availability of nutrients in the soil is a bit more complex and not always sufficient. Of course, this does ignore 1) root tabs that are placed strategically will likely better target root uptake over what's just there in the bulk soil and 2) the fact that I'm sure this system is NOT algae free

I do understand the concerns with dosing nutrients that are accidentally available for unwanted algal/bacterial growth...but at the same time water column dosing is, at least in my opinion, far easier to quantify and monitor because water chemistry is a bit more straightforward than soils...and that's particularly true when you look at what methodology is available for hobbyists. I'm sure you're also familiar with many dosing strategies in the FW world that advocate for "overdosing" the water column, and I've seen algae-free tanks using that method as well. But usually those are essentially tanks on steroids, pumping out huge growth rates with high light and carbon supplementation...

Me? I always get algae, no matter what it seems...I've resigned to that fact despite the fact that I can spew all this theory without anything to really show for it. I think it's an interesting topic, for sure...people will be "debating" nutrients and aquariums forever

In any case, I'm following what you're doing with this setup, whichever route you take, because I'm jealous you get to do this on a much, MUCH bigger scale than I...

 

[Michael Hoaster]

jpappy789, it's funny because I was just reading articles online, and the one you mentioned was one of them. It seems seagrasses are adaptable to varying conditions, allowing them to use their leaves for nutrient uptake if they are more bioavailable in the water than the sediments.

I also reread some chapters in Diana Walstad's book "Ecology of the Planted Aquarium" and found some tidbits I'd forgotten. She is referring to fresh water plants, so I don't know whether these assessments are also true for salt water seagrasses. Paraphrased, "Aquatic plants, unlike terrestrial ones, prefer ammonia to nitrate. They have to convert nitrate to ammonia at a significant energy cost. Aquatic plants prefer to uptake phosphorus from the substrate via their roots. They prefer to uptake potassium and ammonium through the water via their leaves".

What would really be helpful for me is info pertaining particularly to manatee grass, which is what I want to grow. I guess it's back to the internet!

I agree it's fun to go on about scientific theory, but the proof is in the pudding! I will keep researching, but I still think that at startup, I want to favor substrate nutrients over water nutrients. After the grass gets established (assuming I don't kill it), I will experiment with dosing the water vs the substrate, using the gel caps and different nutrient formulas.

I don't want so much to 'overdrive' plant production as 'coddle' them when first planted. From my experience with fresh water planted tanks, I see this as the most challenging phase. Over time I want them to settle into an equilibrium with the conditions in my tank. Eventually, I should be able to determine which nutrients are limiting growth and dose those.

It's ironic that such a relaxing hobby as aquarium keeping can turn you into an amateur scientist! I wish I'd more attention in school"¦

 

[jpappy789]

I believe Ms. Walstad is correct about NH4 vs NO3...generally the former is preferred in N assimilation depending on what's available.

 

[Michael Hoaster]

I went online to find info specific to the species I want to grow in my tank - Syringodium filiforme or Manatee Grass. Why I didn't do this in the first place is unknown"¦

Here's what I read in various articles/studies:

This plant is adaptable to different substrates - from soft, black mud to firm sand. One study said its' favored substrate is very soft, loose, muddy sand.

It is absent in areas of poor water quality. Increased eutrophication harms it and favors opportunistic macroalgae and detrivores, such as polychaetes.

It is more sensitive to salinity changes than other seagrasses and maximum growth rate occurs at 25 ppt (parts per thousand). This seems rather low in comparison to the ocean's average of 35 ppt.

It favors strong currents as evidenced by more luxurient growth in tidal channels compared to quiet lagoons.

Optimum growth rates occur at light intensities of 200-450 foot candles (or 2152.78 - 4843.76 lumens per square meter) Growth rate is greatly reduced above and below this range.

50 - 60% of its' biomass is underground. Higher root biomass relative to leaf biomass indicates plant adaptation that increases nutrient uptake through increased root surface area in low nutrient sediments. Fertilization of the substrate with nitrogen and phosphorus (plant tabs) increased root and leaf biomass.

Favoring nutrient uptake by roots or by leaves appears to be concentration (or bioavailability) - dependent.

It's limited by nitrogen in terrigenous substrates and phosphorus in carbonate substrates.

 

[3D-Reef]

Sound like Your on the right track now!:thumbsup:I look forward too seeing this tank in the future.

jpappy,Welcome too RC.:wavehand:Glad to have You on the forum!

 

[jpappy789]

Good to see you found some more conclusive studies for your particular needs.

And thanks 3D!

 

[Michael Hoaster]

Thanks guys! I wish I could have found more.

Another interesting thing I read was varying C:N ratios (carbon to nitrogen to phosphorus) in the plant's tissue that averaged around 4000:40:1. This would seem to confirm 3DReef's idea of dosing carbon early on.

So at startup, I'm thinking substrate, some live sand, added live sand critters, as well as some cycling starter bacteria and the manatee grass. I may dose some ammonia to help both tank cycling and nitrogen uptake for the grass. I may also dose vinegar as a carbon source for them. I of course will be very careful and ere on the side of caution with any dosing.

I've been reading about fish-less tank cycling using household ammonia. Sounds like a good idea. As an alternative to that I may introduce 1 piece of uncured live rock, which should also be a good source of ammonia. On second thought, it may also be a good source of algae.

I guess cycling a new marine seagrass tank is for me, uncharted territory. Not a reef tank, not a fish only tank. Probably more like a fresh water planted tank really. It occurs to me now that there may be no rush to get through the nitrogen cycle with all the grass. And I'm in no hurry to introduce fish, so maybe no starter bacteria or ammonia. Any thoughts?

I'll cure all the rock separately. I'm only going to get 50 pounds of it for this 240 gallon tank, to provide bio-diversity, hard-scape and attachment points for some caribbean inverts like sea fans, gorgonians and anemones. The manatee grass will be the star of the show, occupying 1/2 to 2/3 of the substrate.

I can't wait!

 

[jpappy789]

Could you link which papers you read on C:N? It would be greatly appreciated.

I currently only do fishless for FW if I'm in a situation where I have to completely cycle from scratch. Even if I'm transferring some seeded media to a new tank I pretty much always add some ammonia first and make sure things run through like they should...maybe a bit much, but I like to play it safe.

By "uncured" rock do you mean that it still has some decomposing organisms left in it? Or would it essentially be organic-free? I'm not up on the slang.

 

[Michael Hoaster]

Here's the link:

http://www.geraceresearchcentre.com/pdfs/1stBotany/1_Short_1stBotany.pdf

Looks like I was off on that ratio-I guessed from memory, or it could have been another study of another area.

Yes, uncured live rock has stuff dying off on it, but a lot also survives, so you get more biodiversity with it. You just have to cure it yourself. If you put dry sand in the bottom of the curing vessel you'll get some tiny critters migrating into it and, voila! live sand!

Hope that helps!

 

[3D-Reef]

I went back through My notes and if Your wanting to dose a N source You might look into glutamic acid.There is a formula in the study by Ehringer and Anderson called Seagrass transplanting and restoration in Tampa Bay.

 

[Michael Hoaster]

I found that study. Pretty Cool! they made a seagrass formula out of prilled nitrogen and other stuff. They never mentioned glutamic acid, but I looked it up. Main ingredient in auxigrow.

I could use more info. Can you expand? Why do you recommend, with other, easier to get materials out there? I mean yes, they had success with it. Have you used it in your tank? Anything you can pass along would be great.

 

[3D-Reef]

There have been many studies done trying to come up with a pathway to encourage grasses to grow/regrow, transplanting,ect.All of the attempts using different sources/combo's of nutrients and fertilizers have failed.Except for the glutamic acid.So far as I know it's the only one to actually stimulate the formation of new growth tips.

I have another study around here some where I'll see if I can find it.It may have been in the seagrass book.I'll do some looking.:fun4:It's been a couple of years since I have seen it though.

I haven't tried it on My tanks.It sounded pretty expensive,plus I didn't need 100 gallons of ferts for a 130 gallon tank.

 

[3D-Reef]

I found that study. Pretty Cool! they made a seagrass formula out of prilled nitrogen and other stuff. They never mentioned glutamic acid, but I looked it up. Main ingredient in auxigrow.

:headwallblue:Your right! It's gibberellic acid in the study.Serves Me right for trying to remember rather than look it up.

In the seagrass book it says "Concerning nitrogen,urea is an effective nitrogen source in seawweeds, but not in seagrasses.However,some amino acids (glutamic acid) can contribute to seagrass N nutrition (Bird et al.,1998)."

An other interesting read...

Production of rhizome meristems by thalassia testudinum Dawes and Andorfer