Yeah, that does sound like a behavioral quirk rather than a physical problem, I environmental concern, or health issue of some sort. Of course, different seahorses do have different personalities and eating behaviors. The individual personalities of seahorses naturally extend to their feeding habits. Some are aggressive feeders that will boldly snatch food from your fingers, while some are shy and secretive, feeding only when they think they’re not being observed. Some like to slurp up Mysis while it’s swirling through the water column, and some will only take Mysis off the bottom of the tank. Some are voracious pigs that greedily scarf up everything in sight, and some are slow, deliberate feeders that painstakingly examine every morsel of Mysis before they accept or reject it. Some eat like horses and some eat like birds.
But it sounds like you’re filly’s appetite only slows down when she is receiving unwanted attention from the stallion and she’s feeling a little persecuted by her persistent paramour. (I’m sure that’s a situation all you young ladies can relate to; surely you’ve all been hit on by someone in which you had no interest whatsoever, and who could never quite accept that fact. Some guys are completely oblivious in that situation, and will keep trying no matter how many times you shoot them down. You know how it goes — sometimes there comes a point where you will go out of your way to avoid this clueless clown whenever you see him coming in an effort to stave off his relentless advances.)
It sounds like your female has reached that point with this particular male, Cindy. Sometimes when their hormones are flowing and they are caught up in a surge of testosterone, an oversexed stallion can become too much to handle for an unreceptive female, particularly when rival males are aggressively competing for mates.
For example, I’ve seen overzealous males swim right over the female, trampling her underfoot in their haste to get at their adversary, and woe to the luckless lady who gets caught in the crossfire between two sparring males (Vincent, 1990). She will certainly be snapped at inadvertently, and may even find herself stuck smack dab in the middle of a tail-wrestling tug-o-war, pulled in opposite directions by her admirers — the same sort of rough treatment Olive Oyl so often received from Popeye and Bluto in the cartoons.
In self-defense, the harassed female often attempts to evade sparring males by darkening and flattening herself against the bottom in submission, or by swimming to the top and suspending high in the water column in order to escape the notice of her pumped-up paramours, since courtship and competition take place on the bottom and seahorses seldom look upwards when grappling with a rival. But in the close confines of the aquarium, it is impossible for a female to escape the attention of her over-sexed suitors for long, and even submissive females sometimes get dragged around the tank by rival males in the heat of combat…
So if she only takes to hiding and goes off her feed a bit when she is trying to stay away from an overeager male, that’s perfectly normal and nothing to be concerned about. One of these days, when she is in the mood, she will respond positively to the advances of one of the males, and everything will work itself out. Once she forms a pair bond with a particular male, her sporadic hiding should cease to be a problem.
Best of luck with your seagoing Casanovas, Cindy!