Um, what power adapters lol?
Most likely you are referring to DC power adapters that are something like 12v or 24v (or any voltage) that are used for powering and charging various electronic devices like cell phones, laptops, or toy trainsets etc.
Those, alone, will not reliably power LED's such that you can use them over an aquarium of any size.
They are not "constant current" (CC) but rather "constant voltage" (CV) sources. High power LEDs really need to be put on a constant current driver for reliable operation.
There are times that you can run some LEDs on a CV power adapter, but you have to get VERY lucky in the actual voltage output. I've run some of the 20-watt chinese LEDs on 12v DC power adapters (CV) because those LEDs have a wide voltage range (12-14v) and most 12v DC adapters put out actually around 13-14 volts.
But even then --- in terms of brightness---- I'm at the mercy of whatever the voltage from the adapter actually is. Even a minute variation in the driver's voltage output will cause the LED to draw DRASTICALLY varying amounts of current.
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