I am glad you are researching SHs before you attempt to do anything with them.
Depends on what species you buy. Pygmy and dwarf need a small tank, mysis shrimp with extra nutrition,covered intake.
Small horses should not have live rock or live sand due to the little critters that can sting them and kill them.
Larger SHs can not survive on mysis and need brine shrimp. The mysis are too small to satisfy a larger horses.
h. Erectus, h. Borbouri, and larger need tall tanks.
Don't let anyone at the lfs tell you, 'they eat live foods but you can train them in no time to switch'. If they are not already trained, they probably won't survive until they do.
They need almost perfect water perimeters. You can't slid or put them on hold.
Just read and research and remember that there are always 10 different anwers for every question. Good Luck. email me if you want:
texaseahorses@yahoo.com or
seahorsecorral@aol.com
Our tanks are on SH.org under the 35 gal.