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[APD] RE: SeaGrass

> To begin with, I'm interested in setting up a seagrass tank.  I realize
> this isnt the best forum for a marine plant but its pretty much all I've
> got at present.  The folks at reefcentral.com dont seem to be very
> specific about light requirements, nutrient requirements, etc.  I
> thought I would try here, thinking all the experts in freshwater plants
> might have some ideas for saltwater. 

Some are, some aren't.
Most have ratty looking seagrass.

> After a lot of consideration and research so far I've chosen to try out
> two species - Zostera marina (eelgrass), a temperate species and
> Syringodium filiforme (manatee grass), a more tropical species.  These
> are very similar to Vallisneria species and differ mainly in their
> salinity tolerances and geographic distribution.  It seems in their
> natural habitat they are quite severely limited by both light and CO2. 
> Light requirements for these two species has been noted as a minimum of
> 18-30% of the available surface light. 

That's what most plants deal with. Not really limited.
There's plenty of DIC carbon available, the sea has a lot of HCO3......
Wave action, most of these plants live in 1 meter or less, go check the
waves there.
During some periods of calm flat water, it can occur.
All plants/algae prefer CO2 over HCO3.
But they will switch and do so when needed. Bobbing back and forth with
CO2/HCO3 makes things tougher on them.

> In the marine environment light
> attenuation seems to be a major problem as the light gets absorbed by
> phytoplankton, dissolved organic compounds, etc. 

I suggest you go to the Keys and see for yourself.
There's plenty of light in those beds. Even if you cannot see down, there's
still lots of light past the secchi disc depth.
It's pretty clear most of the time. 

There's not much phytoplankton nor DOC, suspended particles whipped up from
rough seas is the main thing.
Periphyton and competition and overgrowth by macro algae are serious
players. And boaters.......careless fools rip the tracks through the beds
and you can see them all over. Not all boaters are, but there's not that
much policing of that issue, mainly fish and game, they always bug me
thinking I'm illegal spear fishing there, but I hold up seaweeds, they
frown and leave.  

> Does anyone have an
> idea of how to convert this to a needed light intensity measurement - or
> even a wpg guess?  The measurements for surface light intensity aren't
> apparently given in the academic papers I'm seeing published.  

3-6w/gal works, I use 5w/gal and they grew well.
I did not grow Zostera, I've grown manatee grass. It's often in very
shallow protected water, very mulmy, soft mushy sediment. 

> Also, as far as CO2, apparently if enrichment is provided the light
> requirements in seagrass decreases.. 

True. Same for FW plants.  

potentially lowering the amount of
> light needed on a seagrass tank (that is, if I can establish normal
> light level req's at all). 

Light is not the issue , we can easily add enough to grow them. 

 However, normal means of supplementation
> wont be desirable in this tank since the CO2 levels will drop the pH and
> cause some swings during day/night periods. 

So add lots of aeration eg a skimmer/lots of current. 

 Considering the long term
> planned inhabitants, this wont likely be tolerated. 

There ya go.
You can try it without any critters etc like I did.
I did not find much difference vs the CO2 and aeration. 
Most of the plants were macro algae though, not grasses. The macro algae
use large amounts of CaCO3.
Rather than mainly  carbon from CO2, many are mainly CaCO3. 

 Also, dissolved gas
> levels in the aquarium need to remain low enough to discourage gas
> bubble disease (GBD), which these fish are susceptible too. 

I have not found it to be an issue. 
Damsels would not die.

 I was
> considering using Flourish Excel as a carbon source.  Has anyone used
> this in a marine environment before?  Any ideas on interactions?

It was not intended as such, I'm not sure if it would effect marine
animals, I doubt that's been tested.
Do you want to be the first? hehe

If you take things in stages rather than rushing in and potentially killing
everything, you can find out if it works first, then take it to the
following step next. 
Excel may be useful for a marine planted tank, small amounts of CO2 as
well, aeration and surges seem to work better.
I added Excel a few times. I did not see much but I did not use it on
seagrasses only tank.

Main thing is the substrate for the segrasses, patience, some organic
matter, very fine aragonite and I also used onyx sand, this seems better,
it's mainly calcite and trace metals.

Keep the Ca/Alk up and dose traces every 2-3 days.
Once they start growing they do grow fast and get big, 24" deep is needed
for many species, the manatee grass will get about 12" or so. 

I never did an exclusive seagrass tank, I've seen enough seagrass in my
life for several lifetimes already. I'm more interested in the macro algae
from those regions.
If you are really interested I have a marine plant fest each year and we
are doing a Keys trip to see mangrove forest underwater and reef, and of
course  everywhere there is seagrass(Thalassia and Syringodium). We find
roughly 50 species. It's limited to 15 people, we stay at a dorm like
marine station right on the water, which runs about 25$ a day for 3 days so
this can be done cheap. Lots of island hopping. Folks need to be able to
swim and stand being in the water for a few hours snorkeling around hunting
for plants.The previous 3 days, there is a FW version up north about 6
hours that takes folks down all the FW springs and rivers in FL to see weed
choked rivers full of fish, turtles everywhere.  

> I really appreciate any help and ideas!  Thanks!
> >Sarah

Tom Barr

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