I've had trout in my pond for the winter for a number of years.BUT I also have other species of fish. I have just run the diffuser in shallow water and have seen no downside to it.

Just remember the word "tolerate". Trout grow best around 50°F, the further away from that you get the slower they grow.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).