Is my tank big enough?

[MagicGirl33]

I have a five gallon tank with 4 pea puffers in it, and at first I thought it seemed small but I've done many water tests and it seems fine. They don't pick on each other at all but, a family member purchased three otos. Should I buy a whole new 10 gallon tank just for them? Or should I leave them? There's plenty of algae in the tank for them to eat I'm just not really sure if the tanks big enough. I've heard mixed reveiws.

 

[Colin_T]

A bigger tank is always better. Get a 20 high, it has a similar surface area to a 10