Seagrass Troubleshooting

[tcmfish]

I have been trying to keep Syringodium and Thalassia will little success.

I have been trying to inject CO2 and just started with dry fertilizer but nothing seems to jumpstart growth. I also added in some houseplant root tabs below the sand.

Side note I added caulerpa prolifera and it hasn't grown much either.

Lighting is two 400w metal halide bulbs. Sand bed is 6" deep using a mixture of new and old sand. Tank is probably 150 gallons, on a much larger system. The system has sharks, rays, reef fish, seahorses, etc. probably in the 2000gal range. I was hoping the food that goes into the other animals would help fuel the seagrass growth...

Animals in the tank include an Argi Angelfish, Longnose Butterflyfish, various Escenius blennies (tailspot and blue and gold), a couple gambusia, ghost shrimp, alligator pipefish pair, some astrea snails, couple fighting conchs, and a couple common sea cucumbers.

Any other input would be appreciated, if you need more info let me know.

 

[Michael Hoaster]

I too am keeping manatee grass and turtle grass, as well as shoal grass. My tank is just getting to six weeks old, so I can't speak from years of experience. But I have done a lot of reading! And my grasses are growing. The "Old Favorites", here in this forum is a great place to start.

One mistake I think a lot of people make is to give the plants too much, too early. In fact seagrasses flourish in very nutrient poor conditions. I was shocked to read that they outcompete macro and micro algae, by needing far less nutrients than them. I would have thought the opposite!

So really, seagrasses should be maintained in similar conditions to corals. Then, once they get established and really take off, they'll have the capacity to utilize more nutrients. Another thing to consider is their C-N-P ratios (Carbon-Nitrogen-Phosphorus). I think the average seagrass ratio is around 400-40-1. (Don't quote me on that one!)

Since your grass tank is connected to a large fish tank, I'm guessing you might have way too much phosphate and nitrate. You've no doubt heard of carbon dosing. This is done to get c-n-p ratios for bacteria optimized, reducing nitrate and phosphate. So you may need to reduce phosphate and nitrate and increase carbon, to get optimal conditions for your grasses. Lots of ways to get there - vodka/vinegar dosing, phosphate absorption media, deep sand beds, algae filters, water changes, etc.

But, since you're connected to a large fish system, you may not be able to get there. So, you might want to consider disconnecting from the rest of your system, so you have more control over what's going on in the grass tank. If that's not an option, consider rapid nutrient uptake macros, like ulva and chaeto.

Those are are few thoughts. I hope they help!

There's also some really helpful info discussed in my thread, "Caribbean Biotope Seagrass Tank".

Good luck to you!

 

[3D-Reef]

Along with Michael's ideas,You might try a dose of iron to see if that helps.If it doesn't...get ready for a micro-algae/phytoplankton explosion
due too the plant tabs.
A side note...a study was done on Co2 injection.And they found that the grasses grew better under low lighting while injecting Co2.With 400w of lighting,IMO,you shouldn't need Co2.