Really, it becomes a non issue unless you are keeping an awful lot of dwarf H. zosterae in the tank.
The tank is too small for normal sized seahorses, and for feeding purposes, probably much too large for anything but a large number of zosterae.
Many people like UV sterilizers but in fact, they only work on anything that stays in the water column and passes through the UV chamber.
Anything with any kind of motive power to resist the flow through the system, or with enough mass to settle in lower flow areas, will not be totally affected/eradicated.
Also, as you mentioned, it adds heat, which doesn't come into play if you use a chiller though.
