Tiger Barbs...
 

What aren't tiger barbs compatible with?

And yes i do know they are aggresive unless not kept in groups

as long as the group is big enough (say 8 minimum) then they can go with pretty much anything ime, that includes angels and other long-finned fish

What size tank would you suggest for 8 of them?

60 litre to start.

If you are getting a group of eight you would have to upgrade at some point in the future though - tiger barbs can get pretty big.

I was going to say something like 30g (120l) but this was a recommendation for them long term, rather than just to start with.

Tiger Barbs will only grow to 3" max normally smaller in captivity.

I've got 6 green tiger barbs in a 90g and there are times I almost think that's too small for them with how much they fly around the tank.

At least 29 gallons for 8. A 40 breeder would be better still (more swimming room) for 10. Add a couple of catfish and you've got a tank.

Something on my mind that piggybacks nicely here. How would y'all rate the viability of a 55 gallon with 8 Tiger barbs and 5 skunk loaches. Figure they're all feisty enough to offset each other, particularly with the size of the shoals? Or does that demand a bigger tank?

i have 7 in a 30 gallon and thats plenty of room for them. they keep well with anyone who is a fast mover with short fins, like zebra danios. i have a mix of green and regular, one of them is the very small variety- they all get along great! but i have heard rumors about them not accepting albino tigers as part of a school.