Cheers - I absolutely hate the 'return or move it on when it gets too big' tactic, I get attached to my fish!
The tank is young and the rockwork is very open, I designed it to allow lots of opportunity for fish to swim around and through for interest, including once corals had grown in some. I'm working on my fish list at the moment which is primarily designed to hold smaller interesting fish - any tang addition would be well down the road from now as I expect it would need to be the last one added?
I initially shortlisted a lawnmower blenny for algae crew, however the tomini tang came up as an option that I felt behaviour wise might be a better match.
With the tank planned to be a softy and LPS mix having it a little more dirty from a tang shouldn't be a big factor - but I am definitely not sure about their mature size and whether the tank would feel a bit too small for one.
Thanks for the response!