How many pipefish/seahorses?

How many could i put in a 46 g? Trying to figure out if it's worth it. It would be just them.

 

Most seahorses will not do very well without a chiller as they like cooler water.Seahorses are less likely to contract Vibrio bacterial infections if the temperature is not allowed to exceed 74°F. This is particularly important if the aquarium contains other species of Syngnathids. I will let our resident seahorse expert chime in to give you specifics on there care and how many you could have.

 

Most seahorses aren't bothered by warmer waters in their natural habitat, but in a closed system like our tanks, cooler means better chances of success when in the range of 68° to 74°. That doesn't mean they CAN'T be kept, or aren't being kept in warmer water, but most attempts in warmer water end with problems.
Next, it's not recommended to keep seahorses with pipefish in our aquaria.
Even keeping the same or different species of seahorses that haven't been bred in the same breeding facility can be problematic
Most attempts (but not all) end in losses to one or both.
You could keep four seahorses of standard size like kuda, reidi, or erectus.
There are links at the bottom of "My Thoughts....." in my signature, that can give you the basics of what you need to know to start the seahorse keeping hobby.