Nitrate Problem

[roadblock]

Hello all, Let me give you a run down of my set-up first:
55 Gal tank
Rena filstar xp2 canister filter
seaclone 100 skimmer
200 watt heater
two powerheads
gamma uv sterilizer
small diy refugium for copepods
60 lbs live sand
75-80lbs live rock
sailfin tang
royal gramma
firefish
goldhead goby
mandarin goby
two cleaner shrimp
coral banded shrimp
sally lightfoot
redstar
pumping xenia
yellow polyps
bubble coral
leather coral
trumpet coral
ph 8.2
ammonia 0
nitrite 0
nitrates 80-100
s.g. 1.021
temp 78
220 watts compact flourescent


As you can see, my nitrates are through the roof. I do 20% percent water changes every two weeks. I run bio media in my canister filter, Could this be the cause of the high nitrates? Also one of my powerheads is set-up to blow across my live rock, could this also be part of the problem? I will be upgrading to a 125 in the next few months so I really don't want to spend alot of money on this set-up if I can help it. any help would be greatly appreciated.

[OrionGirl]

Have you tested your source water? How often do you clean the filter media? Why do you have the UV?

JMO, but I'd pull the UV off, make sure the media is accessible to cleaners, and see what happens. Adding some macro algae to your fuge would likely help as well, but I've heard from a number of people who have nitrate problems with UV's--at a guess, this is because the UV kills off a lot of free floating bacteria and critters, which all decay and contribute to the ammonia and nitrite produced. The bacteria that consume ammonia and nitrite are seldom limited in a tank, but those that consume nitrate often are, so they can never catch up with artificially increased production.

[mogurnda]

I'd point a finger at the canister. Having debris sitting in there for 2 weeks at a time is a good way to add nitrogen to the water. The powerhead sounds fine to me.

Other things to think about:
*Get a better skimmer. I hear that seaclones can skim with the right adjustments, but I bet you'll see a lot more skimmate with a better model.
*Feeding: how much, how often? That's the main source of nitrate and phosphate.