No offense, but if that is all you know so far you have a lot to learn about Seahorses. I would strongly recommend going with a reef before going with Seahorses. In reality, Seahorses don't feed on a lot of pods unless they are a small Seahorse like the H. zosterae. However, though it is rare, if you find a mandarin that is trained onto frozen food or you are willing to do this yourself which takes a lot of time and effort, you can have one as soon as you have stable water. If everything in the tank eats frozen food, fish competing for the same food source won't be much of a problem. Do more research and ask more questions as you continue with your tank plans.
Seahorses do indeed feed on assorted 'pods--even relatively large individuals. That is what they would almost exclusively eat to begin with in the wild--and those habits carry over. I would watch mine do it on a regular basis, especially on fasting days. I can't speak for your experiences, but mine were always actively hunting for food--as do all of the healthy individuals that I've had experience with.
The main conflict is still the mandarin and it isn't terribly often that they switch to frozen foods. In any case, you'd want little to no competition for food with these fish.