Great
seahorses also known as Kelloggi need a much larger tank, at least a 90g. They grow very large, can get to over a foot. 29g just isn't going to work.
Also because of the way kelloggi is bred they are very likely to be carriers for many types of parasites. Many treatments with multiple medications still have not been proven to be that successful in keeping these horses long term. The breeders who are exporting them lable them Tank Raised, but there tanks are net pens in the ocean with hundreds of other seahorses. They are much more of a risk then WC's IMHO. Perhaps you are getting yours direct from a aquaculture facility or home breeder, in which case ignore this paragraph.
For a 29g tank IMO, you should be looking at species like reidi, erectus, barbouri, fuscus, or kuda. There are a few others out there but those are the most widely availbale.
IME buying from an aquaculture facility like seahorsesource.com, can save you a lot of money in the long run with saving the expense of hospital tanks, live foods and medication. True one day the seahorse may get ill and need a hospital tank.
IMO I think you should rethink some of your plans to something that would work for you long term, and still something you can enjoy.
Oh, and liverock is fine for seahorses. The Dwarf species of seahorse, zosterae, are susebtable to things like hydroids often found on liverock which needs to be treated, but any of the other available species are fine with rock. Do kill aiptasia or other stinging hitchikers.
For hitches I like to use macro algaes. It provides not only a hitch but also a water filter. I have also used plastic chains anchored down with liverock, and fake acropora's. Tonga branch rock makes a good hitch if you can still get it in your area.
My seahorse tank doe snot have a filter besides the refugium. I have used protein skimmers in the sump in the past an been happy. Other filters that can incorporate media like carbon, or phos-ban can also be useful. Personally I stay away from cannister because I am to lazy to clean them every week, which really needs to be done.
HTH
