I've now got:
6 tiger barbs
2 clown loaches
2 bala/silver sharks
1 albino bristlenose pleco
2 red tailed sharks

And I would really like:
4 kuhli loaches
2/2+ kribensis

Will they mix?
And plus I don't think 2 red tailed sharks is a good idea...
Help!

red tail and rainbow sharks are territorial and will sometimes fight.

that group of fishes should be ok together as long as the tank is big enough for them and it is well filtered. Also you don't want to add catfish or loaches into a new tank until the filters have established.

Let's start with the basics, what size tank are they in?

Clown Loaches - Like to be in groups of 4+ can grow to 12"

Bala Sharks - Like to be in groups of 3+ can grow to 13"

Red Tailed Sharks - Very territorial so needs to be kept with dissimilar fish that it doesn't consider a threat.

So if your tank is big enough I'd suggest fleshing out what you have first, before adding any new species. Also I would agree that having 2 RT Sharks is probably a bad idea, you may also find that they go after your bala sharks while they are of a comparable size.

Thanks for your comments!
The tank is 160L, and we've been told the clown loaches and tiger barbs may shoal together (Which they do) as they appear similar so they're never lonely, and nor are the silver sharks as they've been 'accepted' by the clown loaches (often seen swimming together).
And plus, we bought the bala sharks at about double the size of the RT sharks, so that should be fine.
But the question I ask now is, can I add 4 kuhli loaches? I love them so much

... Anyone?

if the water is good and the filters established, yes you can add kuhlis

I think you should take out the balas and the clowns will be good for a while as they only grow an inch a year
hope that helps

Personally i wouldn't keep these fish together as you have got quiete a few bottom dwelling fish and if you add the kuhli loach and the kribensis in particular you could end up with a lot of fighting, especially when it comes to the kribensis wanting to breed. They can become very agressive.

Hope things go well!