IMO you are getting the short end of the stick on this trade. Around here you can find jags on every corner and females are usually the undesirables from people growing out to get a good male. Female Festae is worth much more than a small female Jag. I gave my 4inch jag away for free...lol
If jags are what you want, than the value of them in general doesnt matter. It matters what they are valued to you. I would pay 15 for a female jag without giving away a rare fish. So it sounds like he is taking the Festae off your hands and then selling you the jag...lol
That 75 is a good size for the female on her own until you get the 150. i would go either 125-180 tho dont see a point in the taller tanks other than more weight on the glass. She is protecting her 75g and basically telling you that she requires that space for herself. My JD was the MOST AGRESIVE FISH IN THE WORLD in a 55... HE NEEDED IT ALL! Put him in a 90 and he was a church mouse.
Making me think i should keep her. Any ideas on how i could ease her aggression so i can put my pike back in