I agree that your pico tank is too small even for dwarf seahorses. I agree that you don't want an air pump blowing into seahorse tank; this can lend to the appearance of gas bubble disease in your seahorses...you don't want them to get that!
I disagree that a HOB filter is a piece of junk. I keep a pair of h. erectus seahorses in a 20g XT and the only filtration I use is a HOB filter. I do a 10% water change every week and my male is having babies every 16 days like clockwork. This tank is the easiest I have to take care of. No heater, a simple T5 HO fixture and the HOB filter.
With the filter I use filter floss and change it out on water change day. I junked the spinning wheel that came with the filter, and just use the floss.
You know how many electrical plugs are needed to run a reef tank? TONS! lol This sh tank has TWO plugs! The filter and the light.
This reef also contains a red scooter blenny, a yellowhead jawfish (and a DSB), several different types of shrimp, the usual snails and hermits. Gorgonians for hitches, some zoas, and some clove polyps. And, chaeto and a couple different types of macroalgae that I bought from Blake here on RS.
I would say get a larger tank and a different breed of seahorse if you want to keep them.