Ok but what other fish could I add, could I add a tire track eel or a fire eel and are there any other good tank mates, would a black labeo shark be too big for that tank as I there is a big one in my lfs.
This depends on a couple of factors. First being how many clown loaches are you planning on keeping and approx how large will they be when you purchase them? How large is the NTT as well?
Both the clown loaches and NTT will be fairly slow growers so a 150g aquarium should last you a fairly long time if not life for the Clown Loaches though ideally a wider tank would be preferred for the NTT (just assuming you have a 72"x18" aquarium, correct me if I'm wrong) if it reaches +14-16".
I currently keep a 2-3" NTT in a 180g aquarium with a 5" IT, 12" Black Spotted Eel, 5"Giant Gourami and 5" Black Shark and my plan is to upgrade to something +300g in the next two years assuming the stock isn't to disproportionately sized to one another or the tank by then. I would warn against the Black Shark however, I somewhat impulse bought mine, the one fish in the tank that was and of course it's going to and currently does cause the most trouble. They can be surprisingly aggressive at times especially towards fish added after it has established it's place in an aquarium.
My NTT was and is the last fish to be added and while the Black Shark is limited in aggressiveness towards the other tank mates who are larger in total mass he gives a particularly hard time towards the NTT who has only recently started to stand up for itself since taking pellets for the first time and starting putting on some mass itself. If you do decide to go with one please be sure to add it after you have the rest of your stock chosen and established in the tank for a decent amount of time.
I think an Eel could be a very good addition depending on what kind you choose, I've found my Black Spotted Eel to be a phenomenal addition in terms of very low aggression, ready eater and quite active to this point. I'd give them a look if you can find one. The seem to reach about 2" when kept long enough so I would think a 150g with a single NTT and a couple Clown Loaches would be a fairly active and attractive tank (again, wider would be ideal if your aquarium is 18" wide).
Hope this helps.