IDeas for my 20G Specs included!

I moved my Koi Swordtail to my 37 so she can be with the platies, I felt she was lonly so I put her with them. As I sit here my tnk seems to look a little emptyeven with the neons darting all over. I added more plants, I think they are moneywort or pennywort, not sure.

If you want to know the specs here they are:
Temp: 78-82
Filter: Marineland Pengiun 200
Ph: 7.4-7.6
Ammonia: 0 PPM
Nitrite: 0 PPM
Nitrate: 5-10 PPM, depending on the week never higher then 10.
Current Fish Stock: 1 Male Pearl Gourami, 15 Neon Tetras, 2 Kuhli Loaches, 1 (unkillable) Hillstream Loach, 1 lonly male guppy and a few Ramshorn Snails I got for free from work.

I want to add a female Pearl in the tank, would that be ok or should I leave it alone, I really want another Pearl since they have great personality! My male Pearl was shy and hid for a few days till he perked up a lot, he's roughly 3.5-4" thats pretty much their full size.

Here's a pic of the tank:

Anyone any thoughts?

It's going to take me awhile to get a female Pearl.. But I might add more neons or a livebearer or two to brighten it up a little. I have platies in my 37g and my remaining Guppy disappeared in my 20(no body anywhere). Could I be able to do that with two Pearls?

I have middle and top dwellers but no bottom dwellers expect my loaches. I could do a ram? I miss Bolivian Rams, it's hard to find a healthy one.

The hillstream is unkillable, I tried and it just sits there mocking me. It survived Kribs, and everything else.

The female Pearl will have to wait unless I can get one at a different LFS and I'll get a Bolivan when I can, I seem to like them and they will go well in the natural theme I have going. I just picked up some New Life Spectrum to feed my fish, I think it'll be better then feeding them the TetraColor crisps. I got Small Fish Formula and Spectrum Thera +A with Garlic, any thoughts on these foods?