Depends on the size group you want really
A well planted 10G with 3-4 kuhlis and a couple of guppies OR platys Or white clouds for dither fish will work. bUT the water quality has to be top notch. This is the set-up I started out with and I loved them so much I graduated to a 55G loach tank that has 20 black kuhlis(Pangio javanicus) 6 striped kuhlis. It also has yoyo loaches, and hillstream loaches with danios for dither fish. It is also a sand tank. Kuhlis of all kinds really appreciate lots of hiding places, the dither fish are necessary to make them feel safe enough to come out or they will hide all the time and you will never see them. Here are a few kuhlis See you should never get me tling about my kuhlis
So I would be able to fit a few in the tank? What size do you recommend on getting? Is there enough gravel in the bottom of my tank and other hiding places? The ferns are also fully grown. Sorry about all the questions.
You know questions are no problem the gravel is fine although it is funny watching them take sand in their mouth and shoot it out the gill openings while they sift for yummy critters to eat. Most Kuhlis are tiny when you get them so there isn't much choice as to size.