The hardiest seahorse?

I'm still planning out the tank im going to make, but I wanted to get smaller or dwarf seahorses with blennies or something. I have never had seahorses before but I have been reading a lot about them. (I will post my setup before I make) What are the hardiest seahorses (tank bred) max size maybe 3.5 inches? How many can I have per gallon. I want to be able to feed them frozen mysis/ dried brine(I heard not the best). Also any websites with quality seahorse livestock would help too, thanks.

 

For the best source of seahorses you can't beat seahorsesource.com.
Dwarf seahorses should be kept by themselves, or with mysid shrimp but not other fish. They are too small. They also require enriched ongrown bbs live.
There aren't any 3.5"max seahorses available in the hobby at the moment.
If you could find H. fuscus they might max around 4" but It's been a while since I've seen any threads showing them available on the North American Continent.
If you've been reading a lot about them, I'm wondering where you are reading to give you the impression that 3.5" max is available?
For dwarfs, you could keep 20 or 30 in a 5g tank.
For most standard seahorses, it's recommended to keep a pair in 29/30g tank but for each additional pair you need an additional 15g, so that 2 pair need 45g.
There are some that require more and very few that require less. If you could find H. fuscus you could squeeze a pair into a 20g tank.
The two most common seahorses sold for the hobby are erectus and reidi and they get to 6 to 8 inches with the erectus having a much fuller body than the reidi and producing benthic fry instead of pelagic fry like the reidi.
There are some links at the bottom of the "My Thoughts..." page linked in my signature that can give you some insight on the basic needs before starting into seahorse keeping. Links on the seahorse.org site will probably require you becoming a member to be able to read those.
I forgot to mention, tank raised is not true captive bred. True captive bred are raised in commercial salt water or in ocean water properly filtered and treated for pathogens, while tank raised are raised in ocean water that has insufficient filtering and treatment to remove the pathogens.
Tank raised, like wild caught, should be put through a 9 week, 3 drug protocol to deworm them.

 

Seahorses - Hippocampus breviceps
Seahorses - Hippocampus erectus

So if I buy captive bred, I won't have to do the treatment before I put them in the tank? Are any of the smaller seahorses hardier then others? Any I should stay away from? I also thought that it might be a problem if I had a seahorse have like 100 babies, there would have no place to put them Could I get a few females and no males?/Best to get pairs? Thanks for the help btw

 

As I mentioned in my last post, the smaller ones aren't available now. If you look at those links you posted and check "availability" you will find it say's "SOLD OUT", and has been that way for a while.
Of those two though, the H. fuscus (not erectus) is easier because the breviceps needs a chiller.
And yes, any seahorse that is True captive bred doesn't need deworming.
Different species produce different lots of fry and you might have anywhere from about 35 up to over 1000 fry at a time.
There is no problem getting all the same sex.