Kuhli Loach Tank Help

[WiltingSoul]

Okay, since I am constantly finding mixed information on Kuhli loaches, I thought I'd post here to get some help.

I might be getting a 10gal hex tank from a friend & I'd like to turn it into a tropical tank with kuhli loaches. It's got a heater and hood with light, I may have to get a new filter, but I won't know for sure until I get a look at the condition the current one is in. The tank is 18" tall and while I'd like the main focus to be on the kuhli loaches, I'd like to have some other fish included as well if possible. Something that will use the upper space of the tank if that makes sense. So my questions are:

--How many kuhli loaches can I put in the 10gal hex? I've read that 10 gal is the minimum tank size for them. And I know groups of 4 or more are best, but I have yet to find anyone give me a number on how many can go into a 10gal, let alone a 10 gal hex.

--What would be some good community fish that would get along with the kuhlis. I'm looking for fish that will use the upper space in the aquarium, make it pretty, perhaps cycle the tank as well since I've read kuhlis like well established tanks. I would also like to have live plants included in my tank, so I want to stay away from anything that will eat them.

--I know you should have sand as the substrate when you have kuhli loaches because they like to burrow in it, also that I should have plenty of hiding spots for them to destress and hang out.

--We used to have an above ground pool and after selling it we were left with a level pit filled with what they called "sugar sand" that they put under it before installing it. Can this be used in the aquarium if it's washed very well, or would be smarter/safer to just go purchase new sand? It's very fine and feels like beach sand.

--As I mentioned, I would like to have live plants in my tank, so which are recommended? We've got hard water out here and I've heard it's good for the plants, but I'm worried about the effect it may have on any fish I have.

--Our water softener uses salt, or I can bypass that and get water that comes straight from the well. Which is preferred?

That's all I can think of at the moment, if I have any other questions I'll be sure to add them in here. Any other advice you can give me that I may have left out is very much appreciated it. I want to make sure I do this tank the right way. And it will probably be stocked over a bit of time since I'm without a job so I'm going to try and find some odd jobs to do so I can get my fish, lol.

Thanks in advance for your help.

-Kari