The tank capacity for the new tank would be 5-6 pair of adults. I will most likely not have more than 4 pair.
The mandarins would be a nice addition except I do not have enough of a pod population in there yet to support them...maybe some day, but the horses like pod grazing too, so there would have to be a whole bunch.
As far as the hex tank goes, that is pretty ideal as they are taller tanks.
You have to remember that you should "ideally" have 3 times the height as the size of the horse. Most of the Ocean rider horses are bigger horses...they do have some smaller ones.
is a good place to go for tons of info on the captive-bred horses. This is Tracey and David, out of Australia that supply most of the captive-bred horses to the US. Marinedepot and FFexpress get their horses from them. (I think ffexpress even advertises "these are Tracey's babies!" on their captive bred info sheets. Talk about market recognition
As a side note, I have been reading tons of stuff on the OR people not being really helpful or co-operative when something goes wrong with horses or order.......