What's in the 75G? That would be my initial suggestion. Killies can be pecky towards the fins and GBR's are so territorial when they are breeding. I usually advise people to keep them in a minimum of 29g/30G. So let me know what else is in the 75G. While you probably won't see it for days on end (I have a young one in a 72G alone), it will grow nicely in there.
You are right, I would only put him/her in the 75. So, let's see, inhabitants are multiples of:
SAE
Bronze Cories
Albino Cories
Zebra Danios
Koi Angels (maybe a problem?)
Endlers
Dwarf Gouramis (male only)
GBR (but the mating pair are off to the honeymoon tank this weekend)
Three Spot Gouramis
Clown Loaches
Kissing Gourami
Mollies
Fidler Crabs.
Loads of driftwood, and stones, bottom is a mix of gravel and pebbles. Plant are various Anubias, Java Fern, Wisteria, Lotus and quite a bit of Java Moss.
Check out:
http://www.youtube.com/watch?v=bFfogDr4AOA
The CAE have been removed.
Thanks again for your help.
Ian