The Finnex 24/7 cannot be adjusted when in 24/7 mode but can adjusted when just in its normal "on" mode. It's a great light for planted tanks but if you plan on using it at its full capacity (at full power or on 24/7 mode) in most cases you'll probably want to be using either pressurized co2 or a high dosage of excel/glutaraldehyde and ferts. For those with low tech set ups you could play with the intensity until you find that sweet spot while still having the option to ramp it up later down the line if necessary.