I have some t5 ho 24w lights with 6400k bulbs. Now I got them for growing orchids, and can take remember a damn thing about lighting for saltwater, and I've never done freshwater plants.
Your 24 watt 6400K T5HO bulbs will work for freshwater, however remember that T5HO lamps decrease in output substantially after they have been in use for a year.
Your 24 watt 6400K T5HO bulbs will work for freshwater, however remember that T5HO lamps decrease in output substantially after they have been in use for a year.
Typically the light intensity (PAR) decreases. I use power compact lamps (basically a T5HO bent into a "U" shape) on a couple of my tanks and the PAR has dropped from PAR@105 when new to PAR@65 after 12 months. There is some thought that there may be a shift in the spectrum (K) but I don't know if it does or not.
GSAS has a Apogee PAR Meter (Model 510) available to members so we can quantify the light intensity in our tanks.