Can't get Nitrites down?

So I'm new at keeping anything other then goldfish and I have a fairly new tank, 20 gallons, a pleco, a golden snail, a loach, 3 mollies and a red finned shark. All small and young (I plan on a 55 gallon if I can figure this out) my problem is I can't get my nitrites down and idk what I'm doing wrong.

Nitrate: 10
Nitrite: 3.0
Water is soft
Alkalinity: 40
Ph: 6.8

 

How big are the pleco, loach, and shark? Also, when did you set this tank up? What’s your ammonia level?

 

I don't have a way to test ammonia yet I need to pick one up. It's a new tank about 3 weeks and all my fish are under 2 inches

 

Oh well that explains that then. It’s normal and unavoidable to have nitrites right about then. I’d research the nitrogen cycle by clicking the blue words. Also, what kind of Pleco? If you don’t know, could you show me?

 

I don't know what kind. He's really little so I couldn't get a very good pic...

Here's a much better picture of my sucker