I have a pair of Stripeless Tomato's and they are the smaller of the maroons in a 40b and they don't allow any other fish in their tank. They do like bubble nems a lot.Why a Condy? This is not an anemone that clowns host.
The maroon hosts in bubble tips and I’d go with that if you want them to host a nem .
A 15g is small. These clowns get huge. I keep mine in a 40g and it’s kinda small for him and he’s not fully grown.