On Feb 28, 8:29 pm, Deuteros wrote:
I'm growing some tomato plants under a 400 watt metal halide lamp. They
are about three weeks old and several are a few days from blooming. Right
now I have them under 18 hours of light and 6 hours of darkness.

Should I continue to keep them under the MH lamp or should I switch over
to my high pressure sodium lamp? Also, should I change the light schedule
at all?

Tomatoes = long day, since they bear fruit during summer.
I'd switch to HPS anyway, since it costs less to run per
usable lumen.