I've had some on my freshwater planted 55 gallon for the past 3 years and have only lost 1 fish in that time and had zero outbreaks of disease. So I personally haven't seen any adverse effects but hard to say.
I use them, pretty weak ones (half of a pair from my 55 gallon long) on a 54 gallon corner. I know that my shy bgk comes out under moonlights, and my chocolate cichlid looks like it wakes up when I turn the day lights on, so its definitely night-like. Just to be safe a give them one or two nights a week of full darkness.
I experimented with leaving blue LEDs on all night. My fish didn't seem to like it, but I have no actual scientific evidence or anything to back that up.
i just recently added a t5 light to my tank that has 5 or so moonlight led's constantly on if the light is plugged in, and my ghost cats are completely fooled by it. they won't go into night-time mode if any light is on in the tank [even a blue LED light lol] but when the lights go off and the moonlights are on, they do their thing. pretty cool to find this out. my spotted raph catfish even came out. no one seems bothered by it; but i am. they have complete darkness every night x3