She's 8 i believe is what she told me today...
Take it from experience, seahorses wont do very well in that tank. I used to raise seashorses (Dwarf, Reidi, and Erectus and dabbled in Barbouri...) and the most success i had was with 55 gallon or larger tanks. Seahorses are social animals and like to be in groups. They will get easily depressed if you have just one or a few and one doesnt get along with another. And when they get depressed they will starve themselves to death... I've had horses that will come right up to my hand and eat frozen food right off my finger, but i've also had horses that wont eat anything but live brine shrimp and mysis shrimp and the occasional snack or cyclopedes. You cant keep any live coral with them as the coral can sting them. I actually had an acan frag that killed a Reidi on me once... It can be very hard and expensive to keep horses. I would steer clear of seahorses at the moment.
If you really want to do seahorses i would set-up a 10 gallon tank and raise a few dwarf seahorses, but once again these guys are very time consuming!!! You have to feed them live baby brine shrimp, which means you have to hatch a new batch every 2-3 days... And that can take up a good amount of space. And they need to be spot feed about 4-5 times a day. But they are much cheaper than a Reidi, Erectus or Barbouri. A reidi usally runs about $80 each, and an Erectus runs about $50 each, and a Barbouri runs about $70 each (or did when i was into them).... But you can pickup 6 dwarf seahorses for about $30-40 plus shipping.
Thats my .02 worth of advice on seahorses...
As far as suggestions on what to stock the tank wth, i would add some plants like caulerpa, sea brushes, macro algea, maybe a Gorgonian (like the blueberry gorgonian in my avatar), etc. And i would stock it with a Mandarin Goby a few cardinal fish, and maybe a small puffer. then i would maybe add a black and white clown fish and a small rose bubble tip annemone. As far as shrimp and snails i would add a peppermint shrimp, and a good healthy dose of blue and red hermits, and quite a few various snails. And i would add some bright and colorful acan frags!
Thats just my opinion on an ideal 28 gallon cube like your. We all have different visions and tastes so if i were you i would only do something that you really want after all your the one that has to look at the tank on a daily basis! Good luck and keep us posted on what you decide to add to the new tank!