Agreeing with Rayjay here. What you said about not wanting to buy another tank suggests to me that seahorses aren't right for you. They do require a specialized setup; so just having a ten gallon and deciding to turn it into a seahorse tank isn't going to work. You really have to understand their needs and be committed to their very specific care. It's hardly impossible, but if you're serious about seahorses, you really need to think about exactly how you plan to keep them.
For instance, we don't know if your filter is even "dwarf safe". You'll have to hatch and enrich brine shrimp every single day, which is at least 20 minutes once you get good at it. Longer if you don't have that experience. Who will feed them when you are away? If you're gone more than a day, you're going to have to have someone not only willing to feed them but to hatch out brine shrimp.
Rayjay is right to suggest starting there. I don't want to turn you off to keeping dwarf seahorses, but this is something that isn't done on a whim, and that's the impression I'm getting from your posts.
Seahorses are by no means impossible, but they're not something you casually decide to get one day if you want any success.