I strongly reommend a fire eel.
The tyre track eel has a nicer pattern but then a fire eel is the tamest and the most personality.
Fire eels get bigger tan tyre track and also they very rarely eat your fish, unlike tyre track eels do.
Tyre track eels have a very strong tendancey to be very terriotorial and aggresive, also there is a small posibily that he won't like your clown loaches. My tyre track ate my clown loaches
admitidly my tyre track was 14" and my loaches were only 3".
If i were you i would defo get a fire eel although tyre tracks are gorgeous
I admit it can be a very difficult choice.
I have a better Idea. Why not just get a tyre track and a fire eel. Although if you do decided to do this there are a few things that you need to know.
Firstly, becuase tyre track eels are so territoral then you need to put the fire eel in the tank FIRST this is very important, also (you tank is already big so there is no problem there) you need to make sure that there is onle tunnel or somehting that are at each end of the tank so they are as far away from each other as posible.
Secondly when they are first purchased try and buy a big-ish fire eel (15" or so) and when you buy a tyre track eel get one that is as close to half the fire eels length as posible (8" or so). If you do thi then you can have the best of both worlds.