A few questions

I'm a long-time aquarist who's owned a dozen or more aquariums with most
common freshwater creatures at one time or another. I've generally enjoyed
great success with all the fish that I've owned, from Arrowanas to Zebra
Danios! I got out of the hobby over a decade ago, but got back into it
recently when a friend had to get rid of his 55 gallon tank (it was me or
the garbage). So I inherited it, along
with the fish in it. I decided that this time around I'd finally try
monitoring water quality (never used test kits before) and try planting some
live plants (never did before).
So to start with, my tank is 55 gallons - 40" long, 20" tall, 16" wide.
Standard sizing.
I have two single 15 watt 15,000K fluorescent bulbs (low lighting, I know,
but Val and Java moss are flourishing)
adequate heating and filtration (Hang On Back - filter media and active
charcoal)
I have mixed gravel substrate, rocks, and driftwood in the tank (all aged,
all rocks non-porous).

In the tank I have a 10" pleco, 4 3" pictus cats, 2 1-1/2" corys, a 4"
Siamese flying fox (the useless kind), a betta, 3 1" Otocinclus vittatus, 5
1" lemon tetras, 5 small zebra danios, and 5 2" scissortail rasboras. I
have two java ferns, four bunches of val (gigantica and americana) and a
sword plant. Here are my questions:

1- My water quality is interesting. I have a pH of about 7, but I have very
hard water (GH) that has almost no alkalinity (KH)! I thought the two went
together? Add to that a zero level of nitrites, but a 200ppm+ level of
nitrates! I use those all-in-one test strips, and am frankly wondering if
they're working correctly. The nitrate level of 200ppm+ has me wondering.
I've recently introduced several new fish to the tank without any problems.
How can the fish be surviving (and growing, and showing fantastic colors,
and very active) with such high nitrate levels? I try to not overfeed (2x
daily for the surface feeders what they can eat in 20 seconds, 1x tablets
just at lights out for the bottom feeders), and I make 10-20% water changes
each week. Any thoughts on the high nitrate levels? My local water is
treated with chloramine (I use a cholramine bond-breaker), and has no
detectable nitrates. Are there any good products on the market that can
soak up nitrate? Do I just have too many fish?

2- I'm predictably getting a slight algae problem. It has gotten worse when
I left town on business and my wife forgot to turn off the lights. The good
news is that
my vals grew about 4" in those two days!! WOW!! The java ferns also
sprouted nicely, but the sword plant is still predictably light-starved I'm
guessing. I always new my lighting was low, but this was a pleasant
surprise. But as for the excess algae, my flying fox is useless for algae
(all he does is harass the pictus cats- never the cories - and for the
record, my pictus cats DO NOT like to school with each other!), my three
small Otocinclus are too small to make a noticeable dent, and my big common
pleco doesn't eat any of it! It's mostly green algae (some brown), but he
just seems to want to stay in one or two places. I reintroduced him to the
tank two months ago from a 75 gallon tank he was visiting and sharing with
another 10"+ pleco and a Red Devil. He ate like a hog on all the algae for
the first month, but now is almost uninterested in eating (even the food
pellets that he used to go for, or the driftwood in the tank). So do big
plecos generally eat well?

3- Has anyone ever seen a pleco or pictus cat consume a live or dead 2-1/2"
fish? I had a small clown loach disappear, and he was my prime suspect for
the high nitrate levels, because I never found his body (and yes, I checked
under the
rocks). I'm just darn curious as to where he could be, and if he could've
been eaten.

4- Does anyone have any experience on trimming Vals? Mine are starting to
run across the tops of the water, and may need a trimming soon. I've read
mixed
opinions about whether it helps the plant, or stunts its growth, or actually
harms it.

So that's about it. I've visited all of the common web pages (e.g., The
Krib, Planet Catfish, etc.) with some help, but I'm interested in getting a
few opinions here. Thanks for your help!

Tony