I would not get the aquapod they have a tendancy to get very warm, and seahorses need water no warmer than 74-75 degrees. A 29 or 30 gallon tank should do just fine. As far as filtration, I would not have a bio-wheel as your only source of filtration. seahorses are messy eaters, and there will be a lot of waist in your tank. IMO also get a skimmer or a fuge w/ macro algea for nutrient export unless you dont mind doing water changes every couple days.