Caribbean Biotope Seagrass Tank

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Today I pushed a plant tab deep into my DSB, near some manatee grass. Just one. I want to see how it affects them. I'm still dosing nitrate and CO2. I'm still tweaking the soup, trying to get the seagrasses to grow and multiply faster. We'll see!
 
I dosed nothing today, save for the CO2. I just observed. It appears that the yellowing came back a little. I will resume nitrate dosing tomorrow, and see if that has an effect. If it does, that points to nitrogen limitation. If not, I'm next going to look at magnesium.

I have magnesium chloride on the way, in the mail. I'll use it and magnesium sulfate to make up my magnesium dosing formula. Magnesium is another possible limiting nutrient.

One of these days I will find the magic formula for prolific seagrass growth. I know I've made progress but it is slow. Complicating this endeavor is the macro algae. It's doing great, but I wonder if it isn't taking up nutrients faster than the grasses can get to them. This brings me back to the idea of dosing the substrate, rather than the water. That's why I added a plant tab yesterday. To test the theory. I want the grasses to get 'first dibs' on the goodies I add for them. If substrate dosing proves helpful, then I'll explore it further.
 
I resumed nitrate dosing today. I think the grasses got less yellow. That points to nitrogen limitation. I will continue dosing the water, and I'll consider substrate dosing. I want the seagrasses to get the first shot at the goodies.
 
Hello,

I have been growing seagrasses for about six months now. I am using the grasses for scientific research. I have been searching the web for two specific species: Halophila ovalis and Halophila minor. I have doubts anyone of this forum would have Halophila minor, but if you have either H. ovalis or H. minor, please contact me. I will pay you to ship a small frag of your grasses or will trade you for the grass I have (please PM if you are interested). If you choose to send the grasses free of charge, your name will be included in a special 'thank you' if any research becomes published. Thank you for reading.
 
Thanks for your response.

Most of the details have to remain private for now. What I can tell you is that getting the seagrass to grow vigorously has been a journey. We are now using carbon dioxide, which has contributed greatly to the success of the plants. This also causes our pH to be somewhat low, which has been frustrating. We are planning on comparing C02 injection with a liquid carbon project to see if that resolves the problem satisfactorily.
 
I too have been injecting CO2, with some success. One other source of carbon (and nitrogen) I have considered is ammonium bicarbonate. I forget where I got the idea. I am dosing potassium nitrate currently, with some success. My manatee grass has grown nice and tall, but I'm not getting rhizome growth/new shoots, which I desperately want. Since my grasses are competing with macro algae, I'm looking into substrate fertilization to give them an edge.

Anything else you can share would be great! Thanks!
 
Thanks, that's a great suggestion. What we have found so far is that our initial concept of allowing the water column to be depleted of nutrients (using macroalgae) and using substrate fertilizers for the grass is ineffective. While this method did reduce diatoms and cyanobacteria to low levels, growth of the seagrass remained very slow until nutrients in the water column were raised. We still use macroalgae to compete with the microalgaes, but we are hoping to remove these once a sufficient amount of seagrass has spread. Water flow seems to be a key variable in keeping both diatoms and cyanobacteria low. The next step in our project will be to move everything to a bare bottom tank in individual pots.
 
Good to know about the substrate dosing, thanks.

Why would you put them in pots? The only reason I can think of, is to sell them this way, along with their own 'personalized' soil. It would be great to be able to buy them this way.
 
Keeping the tank bare bottom will allow us to scrub for algae more thoroughly as well as have more individualized specimens rather than one late lump of grass.
 
I see. I have to remember that what you are doing is for research, not display.

I'd love to hear more. Please drop by and give us an update anytime.
 
My caulerpa is overtaking the tank again. The growth rate seems exponential. I'm not making it from one weekend to the next, without having to crop. I need to do a big export, and get ahead of it. Surely the seagrasses are getting some of the nutrients I'm dosing. It's just hard to tell, in comparison. Dosed a little iron today, along with the nitrate.

My magnesium chloride arrived today, so I'll make some up and give it a go. I kind of doubt magnesium is a problem, but you never know. My wife can use it in her tub if I don't.

I still think the grasses are nitrogen limited. I think the caulerpa absorbs it quicker. I think the key is to reduce its biomass, in relation to the grasses. I think a lot…


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So.. here's an interesting observation from my summer dive and snorkeling in Cancun.

There are zones where each kind of algae has dominance. Where the sea grasses are, there is no caulerpa. Where there is turtle grass, there's no branchy coralline, etc...

The zones can all be within 100ft of each other, but they don't overlap.

I don't really know why that is - just an observation of algae dominance.
 
You may need to put a tang in there... it'll go after the caulerpa first as it's the most tender. It would likely go through it pretty quickly though. Would be the easiest way to get rid of it. I'm not sure you can have that with the other macros... it's too fast-growing. Besides, you don't want it to get to a reproductive phase.
 
Very interesting, Karim. You really got a lot out of that trip! Man, I need a snorkeling trip!

Could you tell whether the different zones were divided by depth (light), or water movement velocity?
 
Thanks, McPuff. A few pages back, there was much discussion on the possibility of adding an Atlantic Blue Tang. That was my concern, that it would go through it quickly. But, that was also before I began dosing nitrate and iron. Now I have explosive growth, and I could use some help cropping it back. So I'm definitely leaning towards getting one. Keeping the macros cropped back might be the key to getting my seagrasses to take off. My biggest fear is that a tang might go after the grasses, once the macros are exhausted. But I think they'd be more interested any algae growing on the seagrasses, rather then the seagrasses themselves.

One other concern I have is order of introduction. My original plan was to add a tang last. Adding one now, second only to the Barnacle Blennies, could be problematic. But since it would be the only herbivorous fish, it might work just fine. A possible plus of adding it so early, would be its effect on later additions of schooling fish. Having a bigger fish in the tank will encourage schooling fish to 'stay in school'.
 
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