my pond's are as wide and deep as the streams that they come from so size isnt the problem i have somewhere around 5000 gallons total. with alot of shade and oxygenation. plus so many plants i can hardly see my fish unless i trim them back once a month. more than likely brook trout and not rainbow. The life expectancy on brook trout is only 3 years in the wild so they only grow 8 inches but if they thrive in my pond they may spawn and ill call some of the trout fisherman to come fish them out and let some of the wild ones go. just trying to do my part to help the trout population. (i would never re release the fish i have had in my pond, i would feed them to the rest of my fish first) if the dnr have a problem with my kids catching some baby fish out of a stream where in 1/2 mile we saw about 50 fisherman all catching boatloads of fish then they have there prioritys mixed up. they need to be working on growing more fish or enforcing length and quantity limits. not internet tracking someone that threw some minnows into his home pond that his 6, 7, and 9 year old kids caught when they were on a hike.