30g tall is to small for a tang. Tangs like length to swim in 6 feet long, 180g, is ideal for a tang. Minimum 90g for smaller tangs like a kole tang.
A 14g is small for seahorses, never mind garden eels. The 30g tall would be a much better environment for seahorses.
As for garden eels if you want to keep a group of them they do best with minimum flow, 6 inch sandbed in a 100g or lager tank. Info on garden eels.
http://www.aquariumdomain.com/viewSp...ine.php?id=184
http://sea.sheddaquarium.org/sea/fact_sheets.asp?id=108
Can't help but wonder (since you have one post) if you are for real and honestly don't know any better or just attempting to get a rise out of people for having and talking about inappropriate set ups.