What you and we need to know is the GH and pH of your source water, presumably tap water, on its own. GH will not change much in an aquarium (unless you target it somehow) and pH might, depending upon the GH (KH also enters this, but we can leave that for the present). Contact your water authority (they may have a website) for the GH (general or total hardness) and pH. This is what you begin with, and selecting fish species suited to the parameters makes life much simpler for you and healthier for the fish.
Adjusting GH/pH is not easy, but without knowing the starting point there is no benefit to going into this now. Water chemistry is a very complex subject.
We cannot offer much about fish species until we know the GH and pH.
This tank is not large enough for this species. Data here:
http://www.seriouslyfish.com/species/crossocheilus-langei/
As you will see, a group needs a 150 cm (5-foot) tank.
This is a good start but with this species I would have more, 10 minimum, half male/female. It would be crowded in this tank though, as it needs a 120 cm (4-foot) tank minimum.
This is a shoaling species (all loaches are shoaling) so it needs a group. Alone it will be seriously stressed, leading to health issues and guaranteed a shorter lifespan because of this. A group of at least five or six would be OK. They need chunks of wood for refuge, and sand which you have (good). They are rather nocturnal by nature, so unless it is well settled with a good sized group, don't count on seeing it much if at all. It is under stress.