So, get some Safe Start and follow all the directions on the bottle. Keep an eye on your water parameters , and consider holding off getting additional fish until your tank has cycled.
Alright I got an ok at the water testing and I have six neon tetras what should I add next?
So does that mean you now have 11 neon tetras? (5 from the OP plus 6 more)
If you wanted an all tetra tank, you could add 6 Von Rio tetras, (they tend to hug the bottom) and then another group of 6 after those settle.
Or you could keep adding Neons.
Or you could add a group of Panda or other cooler water Cory.
*Note the ORs and choose from the options.
No there’s only six in the tank
Should I get one more and call it a day?
Your tank. If that's what you want to do, it's fine. By understocking you will have cleaner water and a different aesthetic than if you push stocking limits.
You can always add in later.
Could I add a centerpiece fish as well?
Depends on what, if anything else you add, but yes, of course that's an option.
So what’s a good centerpiece?
By definition, a centerpiece is any fish that draws the eye. In a 20 gallon you are fairly restricted to the small types of gourami or cichild or platy, dwarf forms of molly, or other livebearer like fancy male guppy.