I'm certainly no expert, but I do have a seahorse tank with 3 Kudas. I would not do it. Seahorses need pretty heavy and frequent feeding which means a lot of attention to keeping the tank clean. Also most people keep their fuge in an unseen area, and if you have ponies you want them somewhere you can enjoy them. I don't think you really want that in a fuge. Also I agree with them wanting some dark time to sleep.
Just my 2 cents, but I would get a dedicated seahorse tank. (I guess that is obvious since I did.)
I thoroughly love mine, but they do take some work and attention particularly to water parameters. Also if you do decide to get them be sure they are captive bred and make sure you see them eating frozen food before you buy.(Mine eat mysis but I'm not that familiar with the little guys.)
Also you could check out seahorse.org . It is a web site and forum just for seahorses and pipefish. The people there may want to offer their opinion.