seahorse question

[orbit]

hi

can someone tell me if its possible to have one seahorse in my 20L tank?

so far i have about 19lbs of live rock and 21 lbs of sand

my stock list so far is
2 clowns
1 peppermint
1 red star
4 snails

i want to add just one more shrimp probably a cleaner

in my tank right so far i have 3 aquaclear and 1 maxijet

i just ordered a corallife skimmer rated for 65 gallon
my temp is a around 78-80 and i have 150W MH

i dont think i want a pair of seahorse maybe just one , is my setup okay?

Thanks
Orbit