Seahorse & Sun coral tank plumbed into larger system

[Muffin87]

I'd like to plumb a small tank into my 115G (Total Volume) softie/LPS tank, so I can keep seahorses and sun corals separately and feed them frozen food automatically.
I'd like to keep just a couple of erectus seahorses, but how small can I go considering nutrients are gonna be shared with, diluted, and filtered by the bigger tank?
Does it have to be 20G or can I go smaller? I was thinking I could go with a tall 15G, something along these dimensions: 14" long x 14" wide x 18" tall.

P.S. I've already sized my chiller to keep both tanks at 73F-74F in the summer.

Thanks!

 

[Rtaylor]

As long as it’s a good size for the livestock. Go as small as you want.

 

[Weasel1960]

I would do some research first. Minimum recommendation for height is 18”. This website has some good info https://seahorsesavvy.com/