Algae eater problems

I'm having problems with algae growth and what I find to be  the inadequate
efforts of 6 algae eating fish to control it.
I have a 55 gallon tank with the a topsoil/vermiculite substrate covered by
about an inch of gravel. It has several pieces of driftwood (one centerpiece
and the rest fragments).
The plants are an Amazon sword, pygmy chain swords, java moss, red ludwigia,
ambulia, foxtail, giant bacopa, water wisteria, and what I think is a red
crypt. wendti. Additionally, there is what has become a sizeable amount of
hornwort floating at the top. My fish load is 5 neon tetras, 2 black neon
tetras, 2 red eye tetras, 1 lemon tetra, 2 white clouds, 1 betta, 1 clown
loach, 1 flying fox, 1 pleco, and 4 otos. I feed them once a day with Tetra
Ruby and freeze-dried blood worms. I've also started putting in cucumber
slices for the clown loach. Filtration is by a Magnum 220 with gravel in the
canister (as per Karen Randall's advice). Additional circulation is provided
by a powerhead. Lighting is from 2 shoplights with 4x40 watt daylight bulbs
on a timer, which keeps them on for 13 hours a day ( the total lighting of
the tank is probably a little lower than 160w though, since the shoplights
don't fit perfectly over the tank). My CO2 fertilization (via the yeast
method) is sporadic and presently I am not adding any CO2 to the water. I do
water changes of about 25% once a week, and vacuum as much debris out as I
can. I don't do anything to the water other than neutralize the chlorine, and
I don't have any exact measurements on hardness or mineral content, but
generally speaking, Philadelphia area water is very hard and very mineral
rich. I've tested the water for nitrate levels with Wardley's test kit, and
the levels are below 10 ppm (non-detectable to the kit). I also tested the pH
with a very old (6+ years) Aquarium Pharmaceuticals kit and it indicated
around 7.4., which is high of course, if the test is giving a reliable

Anyway, my plant growth is quite good in general, but I still have a fair
amount of green hair algae growing on the plants and the glass, and extremely
luxuriant patches of it on the driftwood. Not only are the pleco, otos, and
fox not doing anything much about eliminating existing algae, they don't even
prevent it from spreading or growing back (even on the glass) after I get rid
of it. Its' starting to become a problem on the driftwood, where the growth
is so dense and rich that I can't really do anything to remove it. It looks
nice in moderation, but it's beginning to overgrow things. Only the fox seems
genuinely interested in algae eating, and then only on some of the plants and
not terribly effectively at that. The otos and pleco spend a lot of time
resting on leaves and the bottom (maybe they do more at night). Am I
expecting too much out of them? Could they be stressed into inactivity by
something? With the nitrate levels as low as they are, I would think algae
wouldn't be much of a problem. Is there too much light, perhaps? 

                                Thanks in advance for any help,

                                                 Matt MacGregor