Also find out what your water's pH and hardness is. :)
Kuhli loaches a standard 25 gallon with a footprint of 24" x 12" can house these guys, you want to keep a group of 4 or more, also your substrate must be sand, cannot be gravel because these guys are usually buried in the substrate, with gravel they'll get stressed out and even hurt trying to dig themselves into it.
Bristlenose Plecos would also work in a 25 gallon, just one of them.
I also suggest you upgrade your filter, to an AquaClear 30 or even 50! This will keep your filtration capacity very high.