In my own research, sea grasses need;
A very deep sand bed
Moderate to heavy flow
And good strong plant spectrum lighting.
My last tank was going to be a sea grass tank but I tried for a year to get sea grasses and could not get any this far inland. I don’t know how it ships during the seasons that it is in stock on most on line stores. I know that if I could get some now I would grow it at the store i work at so those of us in the mid west could have an easier time getting them. I do have a wide range of macros that sometimes seem hard to get and grow them without trouble. I will help you in anyway that I can jest ask.

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believe nothing, no matter where you read it or who has said it, not even if I have said it, unless it agrees with your own reason and your own common sense.........(buddha)