My current aquarium (15 US gallons, 24"l x 12"w x 13"h) is about six
weeks old. It's fairly well planted with straight vallis, hygrophilla,
camboba, something that was sold to me under the name of "fountain
grass". Yesterday I added some java fern, cryptos (unspecified) and a
few "dwarf rush".

I'd really like to know whether the fountain grass and dwarf rush are
true aquatic plants (this is in Oxford, UK, if that helps in terms of
commonly used names). The shop assistant didn't seem to know, but
assured me that 95% of the plants in that section were true aquatics.
There were at least three plant varieties that I could identify as
being non-aquatics (two species of Dracaena, Hemigraphis). The foutain
grass has been in the tank since I set it up and looks to be in
generally good health. The dwarf rush is looking good but has only
been in there a day... I previously had a Hemigraphis that looked good
for about a week until it rotted.

The other issue I have is that I'd really like to increase the light
levels in there. I presently have 15W, but I feel that's not enough
for the plants I have in there. There is a bit of a brown algae
problem in there and, although I'm aware this is often a problem in
new tanks, it does not appear to be abating, so it could be down to
light levels. The assistant in the shop seemed to be shocked that I'd
want anything more than 15W in that size of tank. Bearing in mind the
depth of water is only 12", should I bother with more than 15W?