Choosing fish for small tank with a betta.

Ok...tried this on MK, lets try it here:

Compatibility and behavior:
- Be compatible with betta splendens. I have a female betta and am trying to get a male betta, it's complicated.
- Compatibility with clown plecos would be preferred because if I get my own place, I will take back my larger tanks and any fish in the apartment tank will go in with my clown plecos.
- Enjoy dense vegetation/ be a slow swimming or shy hiding fish and not be an open water shoaler/swimmer.

Water conditions:
- Enjoy slow moving water currents.
- Tolerate or prefer alkaline and hard water.
- Be ok with/tolerate higher temps that may occur due to the windows.

Diet:
- Not be a voracious plant eater, nibbling plants is OK.
- Predatory is OK, as long as the bettas are safe the fish will accept freeze dried foods.

Misc:
- Be captive bred. I no longer want to get any wild fish, unless it’s a rescue case where the fish have already been purchased and need new homes.
-Tank size is a twenty gal that’s half filled..so basically a ten gal capacity.
So obviously small size.

I did look at oto catfish and it says they prefer fast moving water.
I'm thinking of going with kuhli loaches. We used have a single kuhli loach in a ten gal and si lived a long time and was extremely hardy.

Nasty noob kuhli loach story on how hardy they are:
I was washing the ornaments in warm soapy water and out popped the resident kuhli loach who was hiding in stuff. I removed the kuhli loach and si survived and lived much longer after that.

There's no currents in my tank here as I'm using a tiny internal filter probably rated for a five gal tank.