I think a 265g tank will be excellent for seahorses, provided it is a seahorse only tank. I have a 125 and have 11 seahorses and it is very succesfull. You will have to stay away from most corals however. You can have a broad range and assortment of softies and zoanthids, mushrooms (not the elephant), ricordia, marcos, gorgonians, and the likewise. Stay away from LPS and most sps. SPS in a SH tank is doable, however you jeapordize your coral. Things like birdnest the seahorse will love to hitch to, making the polyps recede. Then you sps dies and it becomes a very nice ornament in your tank! 23 degrees should be fine. I keep mine at 22 right now and everything is flourishing. A feeding station might be the easiest method of feeding in a large tank. What we did is put a large piece of Botryocladia in our center of the tank and turn off all of our pumps during feeding time. Then just put a turkey baster in the water and all 11 SH go straight to the Botryocladia and hitch there and feed. Our seahorses will also "hunt" the floating mysids from elsewhere. I am a little concerned about the flow, but as long as you have low flow areas they should be fine. When i say a low flow area, I do not mean where no water is circulated, i mean it is just very easy for the SH to swim around and do what it pleases. The larger this type of area, the happier your horses will be.