I really don't know, but do lots of research... Some brackish species live in the brackish areas when young, and make their way out to the ocean (full salinity) when mature.
Here's a list of plants that might do well.
"Anacharis", actually members of the genera Egeria, Elodea are either the most common species of aquarium plant or close to it.
*Anubias spp. A large assemblage of African species and cultivars that are very resistant to both salt intrusion and fish predation.
*Bacopa spp., especially B. monniera is found in brackish waters.
Cabomba species. Beautiful, but easily fall apart when moved, and readily eaten. Take care to cut away rubber bands, remove lead weights, and gently plant individual stems if bought in typical "bunches".
*Hornwort, Ceratophyllum demersum et al. spp. (coontail to pond people). Cool and tropical water species occur. Generally unpalatable to brackish water fishes.
Water Sprite, Ceratopteris spp. Amongst my favorite aquarium plants period. Beautiful, undemanding, adaptable. Here Ceratopteris cornuta in a floating phase.
*Cryptocoryne spp., particularly C. ciliata is well-adapted to brackish water.
Echinodorus spp. The Pygmy Chain Sword, E. tenellus is well-regarded as a part-marine species.
Hairgrass, Eleocharis, particularly the more popular E. acicularis. Lives well in cool water, unheated aquariums. Of the 150 or so species, there are ones found in the tropics to the Arctic.
Hygrophila polysperma, Hygrophilia sticta, many others. "Hygros". Distasteful to many brackish fishes. Do check on the individual species requirements. Most prefer pH's no greater than 7.5, some get very large, others more suitable as closely cropped foreground plants. Some occur in red colors. Emergent species. At right, H. polysperma at a wholesale growing facility.
*Microsorium pteropus, Java Fern. One of the best brackish water plant species. In fact, about the only regularly sold aquarium plant that is "naturally" brackish. Slow, but steady grower, attached to wood.
Myriophyllum spp., Foxtails, Parrot Feather.
Banana Plant, Nymphoides sp. Close relatives of water lilies.
*Sagittaria spp. Tough, waxy leaves help this genus of attractive tall and short plant species to resist salt leaching and consumption by brackish fishes.
Vallisneria spp., particularly the "Giant" Val.s, like V. americana, hold up well to browsing and salt intrusion.
*Vesicularia dubyana, Java Moss. Can tolerate low to high light intensity, soft to very hard waters.
I marked the ones I feel to be the most likely with a *.
I would just use crushed coral as a substrate, but that's just me. Calcerous rocks and shells are okay in brackish. The equipment for brackish is pretty much identical to fresh. Be sure to find out the SG for your individual fish. One last thing- maybe consider archer fish rather than monos?