Not to sound hard core, but...AGW (Ain't gonna work). 
Not sure how you ended up with that combo...that 125 will be a bucket in 3 months. Like everyone said, territory/space/incompatibility/stress problems. I wouldn't 'wait' on anything...start preparing to get a couple of 75s (or better) right now. Keep some extra media in the current tank, get it seasoned up so you can transport when things go sideways. And they will. You just want to stay ahead of the curve and not have to react AFTER fish are injured or killed.
Get some 18-30 gallon totes (lids too!) and keep 'em stored. Extra airstones, hose, pumps, the whole deal. I keep fake plants for all tubs and qt to reduce stress. You also want your fish to grow to max size and potential, they need space and clean water for that.
Good luck!

Not sure how you ended up with that combo...that 125 will be a bucket in 3 months. Like everyone said, territory/space/incompatibility/stress problems. I wouldn't 'wait' on anything...start preparing to get a couple of 75s (or better) right now. Keep some extra media in the current tank, get it seasoned up so you can transport when things go sideways. And they will. You just want to stay ahead of the curve and not have to react AFTER fish are injured or killed.
Get some 18-30 gallon totes (lids too!) and keep 'em stored. Extra airstones, hose, pumps, the whole deal. I keep fake plants for all tubs and qt to reduce stress. You also want your fish to grow to max size and potential, they need space and clean water for that.
Good luck!
