Elaine T wrote:
15 watts of light over a 17 gallon tank is not enough light for
Limnophila and I'm surprised you can grow Heteranthera. Under 1 watt

per gallon is considered low lighting when you look at aquatic plant
profiles. Aqua-glo is a poor spectrum for plants too - the light
looks
purplish, right? Lemma will further reduce the light reaching your
plants, so net it out as it starts to grow too much.

I'd suggest you switch your bulb for a full spectrum "daylight" bulb
(5500K to 6700K color temperature) and get some plants better suited
to
low light. You're not going to get a huge reduction in nitrates
without
high lighting and CO2, but more plants will certainly help.

You make an interesting observation Elaine.
I also have an 20W aqua-glo which says that it promotes the growth of
plants.
It's specs are 55Lux and 18K color spectrum.

I don't know if this is the ideal light for a planted tank, but the
more than 10plants that I have in my 33gal tank, and I should say that
only a couple of them reach the top of tank, seem to be doing fine,
they are growing and look healthier.