Are you hoping to trap them against the screen so you can remove them from the tank, of just keep them out of the skimmer? If the latter, it might be wiser to put that on the outside of the box so the seahorses don't get sucked between the teeth in the first place.
However, you might be able to tell if they have the energy to swim back out now that you have that barrier in place.
Also, you might have to clean that frequently to prevent it clogging up with detritus and foods.
However, you might be able to tell if they have the energy to swim back out now that you have that barrier in place.
Also, you might have to clean that frequently to prevent it clogging up with detritus and foods.