I just inherited a 20 gallon long fish tank from a friend (see pic). It has 6 neon tetra, 6 black tetra, 1 scarlet rasbora (he thinks accidentally included with the black tetra), 2 corys.
think i can add any more fish?
I also realize i need to add plants etc for shelter. I was thinking about switching out the gravel for eco complete or fluorite.