Not knowing the skill level of the keeper I really can't recommend keeping them with other fish. Experienced keepers can do this as they take the time to spot feed the horses. Most other fish are able to outcompete a sea horse for food so a species tank is almost always best.
Of course the tank will need to have hitching posts for the horses. What the best post is can depend on the horse but sea grass and certain macro algae work well.
Flow should be enough to move food around but not so strong as to keep the horse from being able to swim from hitching post to hitching post.
Many horses will accept frozen food but often must be weaned off of live food so it's often a good idea to have a brine shrimp breeding station attached to the tank. There are DIY methods, expensive breeders, and a pretty affordable method from TOM for
hatching brine shrimp and continuously feeding them into the tank.
Another consideration is filtration. They need very clean water so the best bet is to have a large sump with macro algae in it and live rock (not rubble, actual rock). You can set the flow rate low. This will allow for minimal rock in the tank (good for display purposes) but still have it's benefits.
Finally (for now) I recommend the tank be kept around 74-76 degrees. Sea horses are prone to certain bacterial infections of the pouch which are exacerbated by warm water. It's been found that keeping them in colder temperatures (the low end of tropical) helps reduce the likelihood of infection.
Lighting is really only important if you use live macro or sea grass as the hitching post. For me an all sand bottom with sea grass is the most attractive sea horse tank. It's kind of like having a marine planted tank, very attractive and allows easy viewing of the horse from all angles without rock getting in the way. Here's a lovely example I found with Google.