I am by no means a seahorse or pipefish expert or anything, but I have a 29 biocube and I would say that as long as you set it up how you would a normal seahorse/pipefish tank it would be good.
Check outt this link to the R2R Seahorse forum. I'm sure you will get all the advice you need to setup up a Seahorse tank in there... with tons of experts who already have seahorse tanks!