I have two gars (spotted and florida) in a 180 with an oscar,RTC,CK,RTCxTSN, and a silver aro... The only aggression ever is the CK attacking the gars everyone in a blue moon. Keep them well fed and you'll be good for a few years.... When the gar starts to swim in patterns and doesn't move naturally look to sell or upgrade. I would even look at maybe going with a 5x3x2 tank and going with 2 gars and an oscar depending on its temperament. and how you feed them (live vs.non live). What was key for me was that the gar was bigger then the oscar but not so big as to where he could eat/really hurt him. Btw my above statements are only true because of that beast filtration you have going for you?? How often will you do water changes/What type of aeration are we looking at btww? This tank sounds cool.
