in your 25gal tank, moonlights would probably reach about 4 inches in there. also, i'm not sure if you'd agree with me but i think most tropical fishes don't grow at regular rates in non-tropical countries as compared to tropical countries. i found that my three spot gouramies grew really slowly when they grew from 3 inches to 5 inches in 6 months...

i think even with controlling temperature in the tank, it's nothing like keeping fish in it's native climate places...
about this topic, i'm now actually doing some research on animal growth in different climates.
pm me if u'd like to help me out by giving me some info on your fish or even turtle growth rates in non-tropical countries and/or tropical countries.
please help me out here... this might be a real cool discovery.
just to let u know... usually, oscar(not beign overfed, and healthty)* grows from 2 inches to 10 inches here in less than 18 months.
red ear slider turtles grow 3 times faster here in malaysia than in USA from what i've found out. also, alligator snapping turtles grow about 4 times faster here than they do in the USA.
*i fed each young oscar(4-5inches) about 10 feeder fish + pellets + superworms each week.