Goonch should grow 1-2" a month so maybe not quite as fast as some of the amazon catfish species but still fast enough to become a problem in a hurry. Dieselmack kept the biggest one I can think of on the forums at somewhere in the 18-20" size range and it was with tank mates for a little bit I think but then they were removed and the cat acclimated to warmer water with very high dissolved oxygen levels. Typically these cats prefer low-mid 70's not the regular tropical 78-84 temps but Diesel had his living in tropical temps after bringing the temp up over several weeks giving the fish time to adapt.
I'd advise not getting one if you've only got a 180 and don't plan on going to a larger tank at least twice that size in the next year. Also like many said it's mostly a show piece so if you can't or won't dedicate a tank to it I'd recommend a smaller bagarius species that might permit tank mates like bagarius bagarius which stay under a foot.
http://www.planetcatfish.com/catelog/species.php?species_id=572