Need some advice

[AC345]

I have a 39 gallon tank and most of my fish are either a tetra or a danio. Specifically I have:

White zebra danio
Striped Zebra danio
Silver tip tetra
Buenos Aires tetra

All in total of about 12?

I'm wanting to add more fish. What are some options to add? I want seemingly non aggressive fish and possibly an algae eater. We don't have any live plants.

 

[milliemouse]

What substrate do you have?

Corydora's are great algae eaters but gravel can cut their barbels which is not good, I own otocinclus catfish which are also great algae eaters, they clean the glass more than anything though!

 

[AC345]

What substrate do you have?

Corydora's are great algae eaters but gravel can cut their barbels which is not good, I own otocinclus catfish which are also great algae eaters, they clean the glass more than anything though!

Red and black gravel.
When we bought the tank we had no knowledge of tanks and the person convinced us that gravel was best. I now know that's probably untrue.