Here's the dig on feeding the seahorse ponies to anything: when captive seahorses have ponies, most of them get sucked into the filter anyway- love em or not, it does take a good bit of effort to capture all the microponies, set up a low-flow tank for them, and feed them and raise them. The first time you see the tiny 2mm seahorses in your tank, the overwhelming maternal/paternal instinct makes you try to raise (save) them. After a few litters, you tend to just let fate decide. If you'll excuse one tasteless joke, the seahorses act like welfare families- they seem to think the more ponies they have, the more benefits they'll get. It does get tiring trying to keep up with them.
While I don't have a prego female octopus to test my theory on feeding seaponies to cephalopods, I'm thinking it'll be unsuccessful: my large briareus is currently living in harmony with the seahorses in question- and doesn't bother them at all.