Plant and Algae suggestions please

[Limbo]

Looking to startup a new ~95G 36x24x25 tank for seahorses.
Was planning to have very tall rock structure in one corner, sloping to sand in the middle and front (just a couple of inches of sand at the front). Sand will be 4-6" deep aragonite, though could be made deeper or shallower. Lighting will be 4x96W PC fixtures. No skimmer, just carbon in a canister and low flow. Needs to be pod and seahorse heaven and operate like a huge fuge

Can anyone help suggest plants or algae to help fill it. I'd prefer not to get anything that may go sexual.

I envisage reds and greens on the rocks of mixed types which allow hitching.
On the sand area, which would be ~20" deep I'd like to have long lengths of green. I think seagrass is the only way to get this, but I could be wrong and my lighting may prevent it. If this height is too much, I could get a shorter tank to make it look "filled". Also considering a long bed at the back and shorter at the front to add another slope.

Any suggestions? All comments welcome.

 

[piercho]

Manatee grass is a tall grass thats easier than some grasses to establish. It can grow from the sand up to the top of your tank. The green leaves are thin, tubular, and pretty tough. Mermaid's fan is a sandbed algae that grew 6 inches and taller in my tank. Some sand-associated Halimedas can also grow quite tall. Both algae are calcified and green, and are easier than seagrass to establish. Both can sporalate, but thinning the algae should prevent it from occuring.

As far as tall alga go, Sargassum can grow from a base anchored at the bottom of your tank to the top, and even drape across the top of the water as its fronds are boyant. Sargassum is a fairly resiliant alga and I've kept it a while and never seen it sporalate.