I caught them both last fall by accident. I had a minnow trap in a stream around the corner at a buddy's place and caught them both at around 1-2" tops. the stream is actually the overflow for three spring fed ponds upstream about 1/2 mile or so. The thing is, they're used to 80 degree water now in my tank, and unless I let them go in the ponds, I'm afraid the water in the stream might shock them too bad and they'll die.
So to answer your question... I was planning on letting them both go in the Erie Canal which is within a mile of my house. I was fishing in there last weekend, and the stream actually dumps into it anyway. it's a lot warmer in there probably near 70-75 degrees now with all the warm weather. If I float them for 15-20 minutes they'll take it ok I'd think.
By no means would I even think about releasing a non-native species in local waters. Bass and sunfush are comon around here and I catch them in the canal all the time. Also thought it'd be a good idea to lower the bio load as I'm about to add 2 YOYO loaches that are growing up in my 30 gallon.